$100 - $150 Upgrade Possible?

Hello Everyone. I've used tom's and this forum as a wealth of knowledge for ages, and now I'm finally getting around to asking my own questions.

I built a rig not quite a year ago without gaming in mind, but as I've been gaming more, i'm toying with the idea of an upgrade.

First of all, my specs:

Q6600 @3.0
Gigabyte P35-DS3R
4GB Mushkin DDR2-800
Corsair VX450 (33A on its single +12V rail)
evga 8800gs 384mb 192-bit

I've overclocked the 8800gs from its factory settings of 550/1375/800 to 660/1675/1000 but its just not quite enough for me. I play mostly Crysis, Far Cry 2, Fallout 3, UT3, etc. I'm trying to figure out what my best bet would be for a noticeable increase in frame rates. I'm not afraid to overclock a card, which is why i bought the 8800gs in the first place -- it was found to be a good, cheap overclocker.

Can i get a noticeable increase from say, a 4770, or a 4850? Or on the other end, a fading 9800GTX+ or its partner, the GTS250?

Also, is an open box from Newegg a good idea when it comes to these cards? Some things i'd take my chances on, but i don't know about a graphics card.

So, any opinions? Will i notice an upgrade from the oc'd 8800gs to xxx for ballpark $100 - $150?

Thanks!

a GST250 or 4770, 4850 will show noticeable FPS improvement over your current 8800GS

open box gpu from newegg are fine as long as you don't need a power adapter that comes in the box. they come with a warranty but sometimes they do not ship with all their adapters. Also, since they dont have a rebate check to see what the new GPU will cost compared to the opened-box, sometimes its actually cheaper after rebate.

the 4850 tends to run toasty compared to previous generations but most of today's new video cards do. I have actually heard good things about the sapphire 4 series cooler. try to look up the card on a legit review site. I rarely trust newegg reviews. Most of them are " i OC the card and it over-heated...it sucks".
looks like a very good card for the price

as for 1GB compared to 512mb on a 4850, it does not make a big difference. the 4870 and up use the extra memory a lot better.

the 4770 are a fine card and come close to 4850 performance but in the USA they are out of stock so you tend to pay a premium for them. Plus, some 4850 cards had their price dropped to 4770 levels.