Well the real question would be can you justify the upgrade? What are the rest of your system specs and what is the typical usage of the system? Do you do a lot of CPU intensive workloads, or use applications that may be heavily multithreaded? I am referring to stuff like photo, audio, or video editing as games today dont really benefit from multiple cores in any real manner (in terms of raw performance), and still most people will be better off with a high speed dual core than a moderately clocked quad core.
Also note that if you are like most gamers today, and are running a 20-22" display putting out 1680x1050 as the native resolution, you are not going to be as cpu limited as users had been in lower resolutions, so your games may benefit from a GPU upgrade more than a CPU upgrade.
The highest end quad core your board currently supports is the 2.6ghz Phenom II 9950, which is a good chip at $130, but it will be out classed by the newer phenom II chips, even the 2.6ghz X4 810 is going to be a faster option, but as it is not currently supported by your board its not a viable one. Honestly if I were in your position I would take advantage of the new X2
7750 and
7850 prices...the OEM 7750 at a mere
$49 is particularly attractive. These chips are very fast, will surpass anything AMD got out of the Athlon64 X2 processors in the past, including the 3.2ghz 6400, and it will do so at stock speeds. The nice thing of course, is these chips are black editions so overclocking from the stock 2.7/2.8ghz clock speeds is a very easy task and I've yet to see one of these chips fail to hit 3ghz, so you have a fair bit to gain.
If you look at this tway, it really is your best value upgrade. You will get a good cpu upgrade without spending a whole lot of money, and you can make your existing platform last until you decide to make the jump to AM3 next year (or later) when you will be required to buy a new board and new DDR3 memory anyway. If you bought a supported quad core, it would really only be worth it to go for a higher clocked offering as something like the $90 AMD 9600 quad core will only be faster than your current chip in heavily multithreaded applications, for the most part your current chip will be as fast, or even faster than a 2.3ghz quad core 9600.
If you buy one of the newer dual cores, you will get a faster chip on all levels, and at under $70 it is not going to cost you much at all. The difference could be spent towards any other upgrades your system might need such as additional ram or a better video card (if needed), and bet of all if Asus does come out with a new bios to add support for some of the newer 45nm quad cores, you wont have any trouble selling off a 7750 or 7850
