Well if you truely have 4k to invest then you should be really good to go. My first suggestion would be to take a look at 600 watt systems. They are much cheaper, they are much more efficient, and will likely work better based on the width of your room. If you go into a hydro store and tell them that you need to buy 6 complete systems and what not, then they should be able to give you a good deal. If your not getting at least 25% off of retail then go someplace else. I scored my dimmable lumatek 600 ballasts for $175/ piece.
Your veg room can be a little smaller for sure and you don't need as much light either. CFL systems are good but IMO, when you start shelling out all that cash for the big, 8 bulb t5 set ups you might as well ust have bought an HID system.
What it really comes down to is the footprint of your grow and watts/ sq. ft. That is where the 600 would probably be a little better for you. A standard 600 throws a USABLE pattern of about 3 x 3.5 feet. Two rows of them in your flower room will yield you a 7' wide growing space and a 1' on each side to get around. There is also the light mover option. When they are well set up a mover works awesome! When you try to work miracles with them they don't work so well. I have three 600's sitting over a 9 foot long and 6' wide space. I have 12 plants in that space. If I wanted to expand I would just make it longer, not wider. While my watts/sq. ft. are in the 54 watts / sq. ft. range, I am growing VERY dense buds and they are quite large. You can check my SCROG off thread in my sig for pictures.
Lastly, I can't over emphasize that you should likely be spending more time figuring out your climate control situation. Lights are the easy part. Maintaining the proper temperature, humidity, co2 concentrations and air movement is much more complicated and arguably, more important. You could have the best lights in the world but if you have cold nights, the plants are still going to stretch.
If I were you I would start doing expansive craigs list searches for electronic ballasts and a PPM co2 controller. Try crazedlist.org.