Would I see a reasonable difference upgrading an Intel Core 2 Duo 1.8 Ghz to an Intel Quad Core 2.66 Ghz?

The CPU, definately yes. For apps that support quad cores you'll fly, for ones that only support dual core you're still running nearly 50% faster!

With RAM, your operating system tries to work out what it needs. If you have 2gb of ram, it keeps the most important things in memory, and then some of the less important stuff. The rest it dumps on the hard drive until it's needed.

When you have 4gb, it can put a lot more of the secondary stuff into memory, rather than the hard drive (hard drives are MUCH slower than RAM).

Basically, your computer tries to work out what you need and gets that off the hard drive, but sometimes it's too slow and it will slow down. The more memory you have the less often it swaps data from memory to hard drive or back, and the more responsive your system feels.

By value do you mean $$$$$ ? E8500 Core2Duo 3.16 ghz = $190 (Newegg) * Q9400 Core2Quad 2.66 ghz = $299 (also Newegg) Their performance can't really be compared -- multithreaded apps would work better on a Core 2 Quad (e.g video encoding) while older apps and most games would run better on the 3.16ghz Core 2 Duo. This is of course, now changing because dual core technology is slowly getting phased out.

It really depends on the game. You should see a difference in games no matter what, but how large the increase is game dependent. If you want to see a real boost in games, get a better GPU or another one for SLI. If you have the money, get a GTX 260 Core 216 for about $170 and you will see all your games fly. I know people who play games like CoD 4 and TF 2 at 700(yes 700)FPS.There resolution is like 1280 x 1024, but it is 700FPS. But, you need a few things for a GTX 260. First, money. Second, a PSU with enough power and amps. Third, 10.5" of free space in your case. Fourth, adequate airflow to cool your hot card. Memory(RAM) really doesn't matter. Stanbony had 2GB in his system with a QX9650 and three GTX 285's and he was getting 75FPS in Crysis.

A major improvement. You will have a better gaming experience with a quad core (especially one that is of higher clocked than your duo core)

Follow the link below and you will be able to see the difference in terms of benchmarks.

Upgrade your ram to 4 gb would be good as well or higher if your motherboard can support.

Lastly, get a better graphics card like a geforce 9800gt, Ati radeon 4770 or higher if you really want to play all the high end games (GTA 4, Crysis)

NO, you will not see a reasonable difference...you will see a MASSIVE difference.

I am assuming that you upgraded from an E4300 to either a Q6600 or Q8400. In either case, you will see remarkable improvement in all areas.

I would go to 4Gb RAM...and get a nicer GPU card, like a 9800GTX+/GTS260...or maybe even a 275GTX...BUT, make sure your PSU will support it and that it will fit into your case. These are BIG cards...about 10.5" long.

For example, I am typing on a Q9650 right now...and I am running Folding@home, BOINC, and writing to you...all at the same time.

u must get the RAM, because the processor is low specially if you like the new GTA4, I had to get a new PC for it:) I know that it sucks to play the GTA on a core2duo!!! Its just not it!!!

By putting the RAM u will get a faster more eligible graphics if u have GTX graphic card but I can see you have a GT card...so, you will have to change the g.card as well, it sucks if you like the gameplay on low, then just put the 4gb but if you like more then that, then get other CPU or at least a new graphic card.

GOOD LUCK my friend!

Dude have a lot 0f difference

u cpu will run more faster

playing high end games will be a bit easier

u may keep many processes running background

yup surely.its 4 cores so obviously a perfrmance increase wll be seen.add mre ram fr bttr gaming response.

definitely!!!

even a core 2 duo 3GHz, you can feel the difference. 2gb is enough but its better to have more.

nice

yeah massive improvement from that alone

if you can get some faster ram as well should provide more bandwidth thats if your mobo can handle it