I assume for the cooled lamps, you mean you also got the bulbs/ballasts, if not you will need to. Probably the cheaper magnetic ballasts will do. I'm not sure what your friend is telling you, but for air cooled lamps, you want air to cool it, by getting a fan. I guess it depends on the size of your hood/tube, but a basic 6" fan should do you up. I personally don't like buying stuff online in general. I'm not even really a paranoid person, but even running a legal (in the eyes of the state) operation, I don't like to leave a paper trail. I actually use websites alot to get general ideas on pricing, but see if you can work out a deal with a local grow shop. I recently started putting together a grow, and basically made an agreement with a hydro store owner to buy all my stuff from him, and he's giving me a 25% discount on everything. With the discounts, I pay probably 5-10% more than I would do buying online for the same name brand stuff, but no wait, and no documentation for big brother. Also dealing with warranties and returns from the budget online stores can be a hassle. If a part fails I can drop it on the counter at the local shop and they will make it right for me. Also all of these store owners also grow, so being able to ask someone in person for advice on what to buy is great.
But for the stuff you will need: (assuming you got ballast/bulb/hood with your 600w lights). I'm gonna use the Sunlight Supply catalog for ease of having everything together, my hydro store gets alot of this stuff. I'll put the MSRP next to the items, keep in mind any store should give you minimum 10% off that price just for showing up.
http://www.sunlightsupply.com/default.aspx
-Light hanging hardware
I would start with a chain hangar from Home Depot until you got used to what you want for raising and lowering your lights. But for about 15 bucks each you can get something like this easy to work with, and what most people use. I personally use 1" tie down straps from Home Depot. Overall cost is about $2.50 per strap. Don't skimp on this though, thats alot of money hanging from your ceiling.
http://www.sunlightsupply.com/p-13031-sungrip-light-hangers-18.aspx
SUNGRIP LIGHT HANGER 1/8 IN (12/CS)(MSRP: $18.95)
-Inline fan
I consider this fan to be pretty middle of the road decent mix of price vs. quality. I use an 8" version personally, not too loud. For fans you can find all price ranges and qualities, just depends on what you are looking for. I guess the main key is how much air it moves.
http://www.sunlightsupply.com/p-11515-ecoplus-supreme-inline-fans.aspx
736605ECOPLUS SUPREME 6IN INLINE FAN 440CFM(MSRP: $173.95)
-Carbon Filter
This guy is optional. If you want to get rid of smells, these things are the best, and probably overall most cost efficient way to deal with them. There are some cheap DIY solutions as well if you look for that forum. You want to make sure this is compatible with your room size, and your fan size.
http://www.sunlightsupply.com/p-12448-phresh-filters.aspx
701005PHRESH FILTER 6" x 16" 400 CFM(MSRP: $171.95)
-Ducting
The is the stuff you use to connect your filter/fan/lamps. Comes in various types/qualities. The key you want to make sure of is that the stuff you use can safely handle large amount of heat. The quantity on the link below is probably overkill for the amount you'll need, but just gives you an idea of what to look for.
http://www.sunlightsupply.com/p-12164-2000-sr-ducting.aspx
7369206" x 25' SR DUCTING (6/CASE)(MSRP: $40.95)
-Timer
You'll probably need 1 of these for each light. Though technically this timer can handle both of your lights, I wouldn't want to put them in it together. Electrical loads is an entire different thread, theres lots of them on this site if you look. You can probably find something cheaper at any regular store in the electrical/lighting section. Target/walmart,home depot. Keep in mind in general you get what you pay for on these.
http://www.sunlightsupply.com/p-12169-titan-controls-apollo-9.aspx
734105TITAN CONTROLS APOLLO 9 DIG. DUAL TIMER(MSRP: $22.95)
-Lighting controller
This is an option for your lighting/timing you might want to consider. With this unit you could plug both of your lights and your fan into this one box, and manage them with 1 timer.
http://www.sunlightsupply.com/p-14065-titan-controls-helios-11.aspx
HELIOS 11 4-LIGHT CONTROLLER 240V(MSRP: $149.95)
-Clone stuff
The easiest way to get started is to get some cuttings from a friends plant. If you are in a grow friendly state, and you are legal, people sell cuttings/clones on Craigslist all the time. I mean there are purists who would tell you to start from seed as part of the learning process, but it really is alot of learning. You should definitly learn it, but Cloning is the way to go to start off. Keep in mind, these are the just tools, you still need to research how to use them.
-Dome
http://www.sunlightsupply.com/p-13037-mondi-mini-greenhouse-7-propagation-dome.aspx
MONDI MINI GREENHOUSE 7" DOME (50/CS)(MSRP: $5.95)
-Rockwool cubes
http://www.sunlightsupply.com/p-12085-root-riot-cubes.aspx
714129ROOT RIOT 50 CUBES 20/CASE(MSRP: $15.95)
Other items:
Duct tape (get the quality foil stuff, the regular grey stuff is cheaper, but never seems to stick well to anything.)
Gorilla tape - This stuff really is awesome. I have stuff hanging from cinderblock walls with this tape, and have no fears about security.
Reflective material - panda film/mylar
Water PH kit - cheap aquarium bottle set will do to start. About $15 and you can get the tester with the adjusting solutions.
I beleive this is everything I can think of so you can BEGIN life in your tent. If you can get some clones rooting in there, then you have another 10-15 days to figure out what you need to get to the next step. Pots/soil and such. You should really do some research to see what you want, if soil growing is even what you want. There is alot more stuff you will find to buy, and you will be surprised how fast $1500 will go. But it is plenty of money to get started on a quality crop.