New GPU Dilemma - Do i wait for the 660ti?

As it says in the title, im currently looking to upgrade my GPU (and PSU/Monitor which i have already decided upon) from a 9800GT, but am unsure whether to hold out for the 660ti.

APPROXIMATE PURCHASE DATE: Within 2-3 months

BUDGET RANGE: ~£160

USAGE FROM MOST TO LEAST IMPORTANT: Games such as D3, BFBC2 and perhaps BF3.

CURRENT GPU AND POWER SUPPLY: Currently have a 9800GT at clock speeds (have OCed a bit though but didnt really give much of a performance increase), Corsair TX650 (650W) PSU.

OTHER RELEVANT SYSTEM SPECS: CPU - Q6600@2.4Ghz (soon to be 3.0Ghz since i just got a Hyper212 Evo), Mobo - Gigabyte GA-P41T-D3 (PCIe 1.1), Memory - 4GB 1333Mhz.

PREFERRED WEBSITE(S) FOR PARTS: Scan.co.uk, Overclockers, Aria, Amazon, pretty much any reliable UK website.

COUNTRY OF ORIGIN: UK

PARTS PREFERENCES: Only Nvidia cards please, I know this makes things tricky but ive had a bad experience with an ATI card in the past and thats kinda put me off them.

OVERCLOCKING: Preferably not

SLI OR CROSSFIRE: Not possible on my mobo, but perhaps when i get a new mobo/cpu/ram next year.

MONITOR RESOLUTION: Just got myself a 1920x1080  

ADDITIONAL COMMENTS: Would like a somewhat lengthy warranty, in the order of ~3 years however this is not that important. The cooling in my case seems alright, although i do not know how my temps compare to other similar setups. Idle CPU ~30-32 Celsius and GPU at ~40 Celsius with Accelero s1 cooler. These are at an estimated 20 degrees Ambient temp (26-28 in case). Both increase to about 45 and 65 max under full load.

Since this is in a relatively long frame of time I am unsure whether to wait for a 660ti or perhaps get another card sooner that I have been looking at. These include a 560ti, 560ti 448 core and a 570. However I could also wait for the 660ti to come out in "hope" for the 500 series prices to fall, and thus get a better deal, as i doubt I will be able to afford ~£200+ for a 660ti. Note also that I have considered, and am opposed to the idea of getting a 480 (Heat, power and older tech). Finally, I wish that my new GPU will last me for quite a while, i dont mind in the future having to play games at medium levels but really I would like to keep this for about 4 years.

Thanks for any replies in advance,
Jonny.