Best GPU to balance my CPU?

So I did a minor upgrade from an OCed E6300 conroe@1.86stock (OCed to 2.4) to a E5300 Pentium Dual Core@ 2.6GHz stock (plan to OC to 3.0)

<I'm giving my E6300 to a friend for free.>

What is a good GPU to balance my system? I'm thinking of a good GPU without GPU overpowering my CPU resulting in a cpu bottleneck.

3870 or 8800GTS 320/640
4830 or 8800GT/9800GT or 8800GTS 512
4850 or 9800GTX/GTX+/GTS250 +1
4870 or GTX260 or 3870x2
My main goal is to balance out my system without GPU or CPU bottlenecking each other to any significant degree.

I think the E5300 can be best paired up with the 4850 or 9800GTX but I'd like to have a 2nd opinion.
1 vote for the 4850 :D

Or maybe I should stick to me 4650 for now...and get a cheap DX11 card when it comes out? Maybe a cheap DX11 card will equal the 4850 in performance.

Then I'll get a higher end DX11 card to replace my GTX260 in my other rig.

Good or bad idea?
Yeah, get an HD4850. With the recent prices it is one of the best deals in memory and will give you great performance at that resolution.
Also, don't OC that chip to just 3 ghz. It should reach 3.3-3.5 ghz just fine even on stock cooling with just a slight increase in voltage. 3.8+ ghz if you get a decent fan/heatsink for it.

I problem is my mobo must be a bad OCer (Biostart TP43). My cpu voltage ranges from 1.104 at idle to
1.264 at it is already approaching the upper end of stock voltage (1.35?). If I OC it beyond 3.0, the mobo will probably auto-volt the cpu at load to over 1.35volts - which I don't want to do since I like to keep voltages at or under stock.

My Biostar T series is supposedly good for OCing...but I can't even change the voltage manually in BIOS. >_<

Your motherboard is a fine overclocker, I've used it myself with an e5200. No motherboard automatically over volts, you have to tell it to. The voltage you are saying is most likely the stock voltage(VID) for your e5300. It varies by individual chip and you can check yours with Core Temp;

The reason your voltage varies is that core 2 duos have a power saving feature that lowers the multiplier/voltage of your CPU when it is idle. This can sometimes cause a high OC to be unstable but the feature can be switched off in the BIOS if necessary.
Basically your voltage is entirely normal and it won't change unless you tell it to. That motherboard lets you increase the voltage by 5% at a time. 5% should make your voltage about 1.325v which is fine and entirely within specs. 10% will make it 1.38 which is outside spec but not to a degree I would worry about at all if you have a decent fan but I would avoid it on stock cooling.
From my experience with the e5200 you might not even need to touch the voltage at all to get it up to the 3.3-3.5 ghz range but bumping it up 5% shouldn't be a concern. Just keep an eye on your temperatures as always when you OC.

thanks a lot. That actually answers a lot of questions from one of my unresolved posts too.

So are you saying that if I want to have it on the lowest possible voltages, I should leave the CPU overvoltage in BIOS on "auto" instead of "+5%, +10%, +15%" ?