I would assume you've looked into it already, but if you have a little bit of free time building your own tent would save a ton of bucks. Go to Home Depot, but some PVC and fittings, some PVC cutters and some good tape. Go online and but some black and white poly (panda film) and a tent zipper, and wah lah. Your very own grow tent exactly the size you want it for under $100.
Then you can spend the rest of your money on a 600w HPS and a vortex exhaust system.
If you must purchase one though, just google reviews for the tent your looking at. If possible get one with a metal frame (or the sturdiest tent you can find).
Thanks for the info, I hadn't really considered building my own tent. I'll have to search for some DIY guides to see what's involved. I'm pretty handy but my time is limited.
Metal frame should be a must IMO, unless you can mount the heavier items to a stud in your ceiling.
Building a room instead of using a tent isn't a shit idea at all. I had the extra time, ability and tools to build it but the simplicity that a tent offered was unbeatable for me. I may be lazier then you OP though.
I definitely want to go with a metal frame, be it a DIY project or a pre-fab tent. I don't want to risk a fire from a collapsed tent. Better safe than sorry IMO.
What would be the best home-made solution for a metal frame? I suppose I could just get some metal pipes and have them cut / threaded at my local hardware store.