On a tight budget you say, honestly your not going to find 775 chips cheap anymore if at all. Ram you can find but DDR2 is again expensive due to the market and DDR2 being obsolite. So good luck to find anything on a tight budget, you may be better off upgrading to a newer processor. Probably a good solution would be to get an AMD processor/mobo/ram combo thats a fraction of the cost all seperate.
DDR2 RAM is actually the same price if not cheaper than DDR3.It's still used more than you think.
Your really not going to find much performance in the 775 socket.It's very outdated.I think the best value for your money would be to upgrade the whole thing.At that resolution games are far more CPU dependant so it makes sense to get a better processor.
IMO it is better if you just keep your rig as it is. if you can just OC your CPU to 3.0Ghz and you should be fine in most game as long as the game are not craze cpu core count. to me it is better for you to get new platform altogether if you want to upgrade your current proc. to most of people LGA775 is already dead.
honestly i don't count on it anymore . LGA775 is not a bad option if you want something that just work for light and moderate task like surfing or doing office work. its pretty cheap to assemble a system based on LGA775 for that purpose. but for someone that want gaming performance AM3 is better if he doesn't have the money to go for intel LGA1155 platform
if you want to make your system zippier,, add a couple more gb of RAM (cheapest) or a SSD (pricier, but more of an increase in performance and you can reuse in a new build when you have the money,, RAM you aren't guaranteed if you have to buy DDR2, then I'd say no)
Try and overclock your CPU, other than that you shouldn't need to do anything to play games well at your resolution. If anything I would buy a new monitor you aren't letting your GTS 450 stretch it's legs, you can play games in medium on a 1080p screen.
I wouldn't bother with the q6600, they aren't all that cheap even used, and your probably don't have a good enough motherboard to overclock it and get it's potential from it.
Yah but the e8400 is $180.You could get a six core for that much money.Hell you could get a 2500k.All i'm saying is that the Phenom Dual Cores can perform very well and come fully loaded with features like L3 Cache for half the cost.Not to mention how easily they can be O.C.'d.