This benchmark is supposedly using one of the 6000 series cards, so I'm really not sure whats the best performance for the money. I play a lot of high-end games like Metro 2033 and STALKER Clear Sky/Call of Pripyat/WoW stuff like that. So I'm looking for something thats going to last.
Final note, it has to be on Newegg.ca, as I'm a Canadian, so USD is a bit too confusing for me.
Some of my thoughts:
1) What resolution will you be gaming at?
2) Read this article, and pick the best card you feel comfortable paying for. http://www.tomshardware.com/reviews/gaming-graphics-rad...
Make certain that it is several tiers better than your current card, or you will be disappointed.
3) Your Antec 900 is a fine case with good cooling. No worries there.
4) Pick a card with a dual slot direct exhaust cooler. Cards with fancy coolers do well in open case benchmarks, but just heat up the case interior if they don't exhaust the hot air directly. This results in higher temperatures for both the vga card and the cpu.
5) Despite the higher number, the 6870 is not as strong as the 5870.
6) If the Canadian dollar is close to the US dollar, consider the GTX470 or GTX480. Their prices are now more competitive since the launch of the GTX580
7) New cards from AMD are due in December, it might pay to wait and see.