Might want to check F&S or Marine Depot (generally pretty good about running specials every now and again) Oddly enough it can depend on what color range you are looking for in T5's, since they have gained such popularity of late the price tags can fluctuate with stock.

9 times out of 10 you'll save big $$$ going the DIY route. Don't try to cut corners on the reflectors though... There is an amazing difference between high end reflectors and the cheap ones. Perpetual has a thread from a while back that really demonstrates this.

Big debate over ballasts, personally I say overdrive them and get every ounce you can, but provide for adequate cooling. But then again I like to soop up everything.