what speed is your ddr2 sdram( 200/400, 266/533, 333/667. 400/800, or 533/1066)?
Does you mobo have overclocking options in the bios?
I might suggest an aftermarket cooler for the C2D e4500 so u can max overclock. At
stock mhz the c2q e4500 would notably bottleneck these cards. If your mobo and
ram are up to it u can clock that cpu from 2.2(11x200)to 2.93(11x266) or higher.
not sure about 3.67(11x333) tho. To do that you would need to mod the memory
ratio of faster ram to run slower and then bump up the base clock so your ram
does not exceed spec. You could well get a base clock speed between 266 and 333
(ie 300),but it is best to run your ram at jedec speeds. Running at non jedec speeds
is likely the best way to get the highest stable oc on your cpu, tho. This requires
your ram to run at least as fast as 333/667 by default(unless you have pretty good
266/533 ram that is made to oc. just maybe loosen the timings a bit and give the
dimms and maybe the cpu a little more juice). btw 300/600 would get ur cpu to 3.3
11x300) which should be totally doable on your cpu. Actually with the right ram and
mobo you may get 2.93 with the intel cooler. If you don't know your ram speed there
are a few ways to find out. reboot and take note of the info that pops up before
windows starts to boot. If the info isn't there, reboot and enter the bios(hit the key
those first screens prompt you to use 4 that)and look around the pages to find out
info on your ram. This will also give you the idea of whether your mobo will allow
things like changing ram ratios, base clock and maybe voltages to which are all
integral to cpu/system overclocking. Sorry, that last bit is kind of wall-of-text-y.
If you can OC, then I'd go with gtx550ti and a decent cpu cooler combined to
stay within you budget. The other cards would bust your budget and be bottle-
necked even more by your cpu , so you don't want to spend extra money on
performance you won't be able to use. If you can get 2.93ghz now, u may be able
to afford a 7770 or 6850(about the same after driver updates for 7770 and it is
cheaper and more overclockable too, but you would see diminishing returns w/o
an even faster cpu).
If your ram is not suited to overclocking, you may be looking at a fairly expensive
route of replacing what you have with faster ddr2 which costs more than ddr3
nowadays, limiting your performance boost for the budget even more. If you
would be wanting to swap in a better cpu, that would cost you since socket 775
flavors are kinda hard to come by now too. No sense upgrading the mobo as it to
would be pretty expensive and require a new copy of windows as well if you are
running an oem version now. Actually if the mobo is ok and you can use the stock
cooler and buy better ram, you could maybe go gtx550ti(assuming your current
ram is not suitable to oc with).
Basically, if your ram and mobo can't oc that e4500 then you wont get much out
of gtx550ti, hd7770 or hd6850. you may be looking at saving up quite a bit more
money to do a proper overall system upgrade. Sorry bout teh redundancies.