Tire Advice!?

Well here are some pics of my balds A$$ tires! i've been putting off buying new ones for way too long. They are pretty bad!. Anyways, i'm buying a new set for the rear sometime this week. I have 17x10 cobra R rims. currently have 245/45/17's all around. i want the widest tire i can fit on the back. how wide can i go? (with and without quad shocks???) not sure if i want to ditch them right now, but i think they may limit me quite a bit. just looking for a good tire for the money... im broke!. cheapest i've found is $450 (for 2) (installed & balanced) for OHT Falken "ZR" ZE512 275/40/17. I also priced out BFG G-Force TA KDWS 98W BSW 275/40/17 $660, and BFG TA KDW 98Y BSW $767. I have heard lots of good stuff about the kdw's, which is why i priced them out. I have a hard time paying that much for 2 tires though!!! any cheaper options?

thats what i think too, but i'm in canada... i just assumed thats what it costs up here. the quotes above aren't even for that great of tires, am i correct? i was shown tires for over $500 each and even more, just for the tire. i see prices in magazines from the states for much less, but by the time shipping and duties etc is added, its not really cheaper for me... it sucks. i'm kinda looking for cheaper brands that aren't crap. at this price, i'll have a hissy fit whenever my tires spin! $$$$$$$!
ps - who makes those e-sigma's you're talking about?

ok, maybe i should have been a bit clearer. i won't be buying those, just wondering the brand name so i can avoid them. ? thanks. anyone with experience with those falkens in my first post above? can i go wider than a 275 with my quads on?