You can produce ~1lb/cycle (8-12weeks) with that foot print.* *Once you learn to grow and become accustomed to your particular strain and grow conditions. You're more likely to hit .5-.75 lb/cycle.
Personally I would recommend you utilize your carpenter. Have him build a well insulated decorative box in the dimensions you want (A box inside a box with insulation). An insulated wooden box will keep temps more constant than the metal lockers but more importantly will kill the sound. Metal cabs tend to amplify all noise and growing pot can be noisy. Not sure what you're carpenter costs but the materials should be cheap (Less than $150 on the cheap with ok looking veneer). If you want to go with a metal cab then here's one
72x36x24 steel locker for $257 with free shipping
http://ibuyofficesupply.com/Products/72-High-Standard-Cabinet--36w-x-24d-x-72h--Black__TNN1480BK.aspx?ref=google&source=google&utm_medium=shopping_engine&utm_source=google&gclid=CPSM5v7r97ICFQSCQgodT0MAcA
You can surely get these cheaper from different sources but here's a 600w dimmable lumatek with aircooled sealed hood and digilux MH and HPS bulbs for $425 -
http://www.urbansunshine.com/index.php?main_page=shopping_cart&number_of_uploads=0
I highly suggest paying for a quality ballast and I highly recommend lumatek. I also recommend digilux as well as lumatek bulbs.
Already you have a better a hood, ballast, bulbs, enclosure, and it's a fraction of the price.
If this is going in an office I would spend your big bucks on a high capacity QUIET fan. I hear S&P makes some very quiet ones. Keep in mind you can get a fan that will grow pot great for ~$50 but it will make a lot of noise. If you want quite be prepared to spend considerably more for a fraction of the CFM. You might consider splitting the exhaust between two smaller (100-150cfm fans) rather than a single 250-400 cfm fan. Same air movement but again less noise.
If you choose to have a lower compartment then I personally would recommend a cheap DIY LED fixture. For $150 you could have 150w of LED which could keep temps down compared to flouros. If you want to go cheap then go with bathroom vanity lights and CFLs. You can of course replicate the grow box with T5s - they work great but might cost you as much as the LEDs.
Not sure if you wanted more details but that's the basics. $500 for good ballast, hood, bulbs. $250 for a metal cab or $150-? for a custom wooden. $50-250 for fans. $20-$150 on veg lights (let me know if you need in instructions/sources for DIY LEDs). You'll spend another $50 on ducting and then there's soil and seeds. So that's on the high end $1200. If you want to go hydro I'd suggest a DIY unit. They are cheap and easy and there are tons and tons of different types/styles. Hydro/soil is a preference point and you are the one to make that choice preferably once you are a more competent grower. I personally would suggest a first time grower to start with soil - preferable an organic follow the recipe super soil (just add water and wallah!). But if you want to really be lazy and buy something you can find cheap hydro kits just like the grow box all over.
From the homedepot there are systems ranging from $30-200, 1 plant to 10:
http://www.homedepot.com/webapp/catalog/servlet/Search?storeId=10051&langId=-1&catalogId=10053&keyword=hydroponic&Ns=None&Ntpr=1&Ntpc=1&selectedCatgry=SEARCH+ALL
If you want a cheap kit like the grow box here's one for $45 with free shipping and media included, just one of many -
http://www.ebay.com/itm/6-SITE-HYDROPONIC-GROW-SYSTEM-KIT-W-NUTRIENTS-Ph-test-/150898412578?pt=LH_DefaultDomain_0&hash=item23223f0c22
As to a scrog... that really depends on plant count, strain, veg time... Yes I think scrogs or at least a bit of LST can be extremely beneficial, especially in a small enclosure.
Hope that helps a little.