The only way that you'd need to replace anything on a mid-specced gaming PC in a year is if, a year from today:

1) A game came out with absolutely insane minimum specs (I'm talking Core-i5, $200+ video card, 6 GB RAM minimum), and

2) Said game happens to be so good that you absolutely must play it.

The chance of this happening is pretty much nil.

You'd have to deliberately buy parts that are currently dated to require any major upgrades on a $900 build in under 18 months. Mostly likely by going with a cheaper CPU (budget dual core), minimal RAM (2GB) and VGA cards that are past peak production (G92 based cards for example).

It may not be long before minimum spec requirements for high end games start requiring quad cores, so dual cores are likely also on the verge of falling out of the "ideal" for gaming systems.

But for example, the gaming system I built just over a year ago for around $1k (including Vista 64 and a quality M/KB) is an E8400 @ 3.9ghz, HD4870 512MB, 4GB DDR2 1000 RAM, 600w PSU. In other words, a build that currently needs nothing in upgrades for gaming at 1920x1080 resolutions.

I have a hard time seeing that changing in the next 6 months.

If anything, that system will only be rebuilt within the next year for the purpose of running productivity software (more Maya and more Premiere/After Effects next semester) as my stock clock Q6600 is already less than ideal for those apps. Unless the updated Q1 offerings from Intel drastically change the price/performance field, I'll be going with an i7/X58 build with either 6 or 12GB DDR3 1600 RAM using a 920 clocked to about 4ghz.

I should note that the 1GB 9600GT I bought about six months prior to putting together the E8400 based system ended up getting replaced by the HD4870 with the 9600GT losing about $100 off retail during that time frame which turned me off to buying lower budget VGA cards for anything other than low budget builds.

Quad-core CPUs are dirt cheap nowadays anyhow, so unless you're on a really tight budget, there's really no reason to not get a quad, or at least a tri-core CPU.

If you buy a dual core CPU today, you are definitely buying "for the moment" which more or less means upgrading sooner, or dealing with a less than ideal set up in the future.

It's still kind of hard to recommend quad core CPUs specifically for gaming since there just aren't many games that optimize for 4 threads or cores. But if you can get one reasonably priced and overclock it to similar speeds used in dual core gaming systems (3.6 - 4.0ghz being the current point of diminishing returns), there's no point in trying to save $100 or less on a lesser CPU that you'll end up replacing much sooner.

For CPU intensive productivity, encoding, 3D software and rendering on the other hand, there is no such thing as "too many cores" or too much clock speed.

Mm, however, DX11's supposed to use more threads better, and there are also games like RE5 and DA:O that love quads.

listen to soleron he knows what hes talking about, and in the most case you dont need anything to terribly good except for a graphics card, my old computer that i use here and there has 2gb ddr2 666 ram in it an AMD 64x2 clocked at 2.6ghz running windows XP but i have an ATI Radeon 4670 and am able to play borderlands on max 1280 x 960 resolution (i know its no crysis), if i had extra money to blow id upgrade my ram and throw in a HD 5850 or 5870. For the most part if your gonna be dedicating it to games id suggest a Phenom 2, at least 2GB of DDR2 1066 or higher ram , and an HD 5850 graphics card. that'll keep you good for quite a while specially since the new radeon cards support direct x 11 all you would need in a few years might be to upgrade the graphics card

Personally, I'd go with nothing but quad core because I use the PC for a lot more than just games, and I will never build another "PC game console" again unless it's for someone else. And it would have to be a low budget system. And I would still strongly recommend against it.

There's no longer any real cost premium associated with quad core CPUs. I'm ignoring the budget sub $100 CPU market here of course.

But if you're still talking "just gaming" everyone knows the best performance for your money still lies in the VGA cards you buy. Of course not many with a whole lot of sense and a decent budget are going to pair a sub $100 CPU with say a $300+ VGA solution.