AMD Radeon HD 6800 series or GTX 550 ti ?

*** Update ***

6800 isn't a specific model, it's a series (or group of cards) just like 4800, 7700 and 5800 series. It's like saying GeForce 500 series.

There wasn't ever a Radeon HD 6800, just the 6850 and 6870. There was a Radeon HD 4830, 4850 and 4870 but never a 4800. Likewise there's a Radeon HD 7750, 7770 and 7790, but no 7700.

So when Windows reports a 6800 series card, it means you've got a 68xx model.

*****

The Radeon card is better.

By how much depends upon the exact model you've got, but even the HD 6850 is better than a GeForce GTX 550 Ti, which is equal to the Radeon HD 7750 or 6770 (which is just a renamed 5770) in most games.

http://www.tomshardware.com/reviews/radeon-hd-6790-barts-gpu-geforce-gtx-460,2917-16.html
http://www.techpowerup.com/reviews/MSI/GTX_650_Power_Edition/7.html
http://www.techpowerup.com/reviews/MSI/GTX_650_Power_Edition/12.html

The Radeon HD 6870 is even better, about equal to a GeForce GTX 650 Ti.

The Radeon HD 6850 & 6870 are much stronger.

The GeForce GTX 550 Ti is just barely better than a Radeon HD 5770 except in Nvidia-optimized games like Starcraft 2 and Portal 2.

http://www.anandtech.com/bench/product/538?vs=541
http://www.anandtech.com/bench/product/539?vs=541

It is not what i might name a well balanced gaming pc, because the CPU is more suited to multithreaded apps like video enhancing or media modifying. It's a strong CPU though, but no longer what i might pay money for just for gaming when you consider that a Core i5 2500k would participate in at the identical stage at a much diminish fee. The equipped video card isn't particularly a excessive end card either, it's extra of a mediocre or mainstream GPU. If which you can customize that computing device, select a Core i5 2500k CPU but prefer a way more strong graphics card, equivalent to a Radeon 6950.

550ti.