The GTX480 might come close but it's really not worth it.That card is very outdated and a huge power hog.I don't think it's a worthy option if you want it to last for 3 years.
I think the best thing you can do is get a 7850.They are decently priced for the performance they offer and leaves enough room in your budget for a good PSU.With a 7850 you can get a steady 30+fps on Ultra but with no A/A or A/F.Honestly though I would rather play on High settings with full A/A and A/F.Isn't a huge difference between Ultra and High.As for Assassins Creed 3 you should have no problem maxing that out.
7850 BF3 Benchmark(notice the settings they used and resolution)http://www.guru3d.com/article/amd-radeon-hd-7850-and-7870-review/21
XFX 7850 $235=$220 after MIR + Free Shipping(2 Free games which is a really good value)http://www.newegg.com/Product/Product.aspx?Item=N82E16814150608
Having problems with my Internet right now so I can't look for a PSU right now.