Mid range AMD or Nvidia GPU?

Jumping right into the subject i am looking to treat my system with a new GPU. However recent events have made my thoughts on what would work best for me very clouded. Things like AMD's Mantle, Nvidia's G-Sync, the whole price to performance things and so on. 

What i am trying to find out is, what brand (not sure if that is the right word to use) would benefit me the most in terms of features. 

 

I currently use my PC to work on, game with old and new games, edit photos with Photoshop Elements 9 (hoping to upgrade to Light room in the next years or so) and multitask a fair amount on 2 monitors (planning to upgrade to 3 in the future).

AMD's Eyefinity feature looks to be fantastic for gaming and productivity but Nvidia's CUDA could provide a boost with Adobe Lightroom photo editing software from what i have understood.

I do not care about things like Advanced Phys-x on Nvidia or hot temps wit the new AMD R series of GPUs as i normally play RTC or Simulator games, and i have very good airflow on my case too. 

Furthermore i am looking at a mid range card that could pull at 1080p on most games at high settings (not necessarily max settings). So if anyone has a recommendation shout out with why and i would be glad to have a read.

Normally i know exactly what hardware i want and why, it is mainly due to the fact that i do not really understand all the new features of the new products and how they would impact the consumer (or how effectively they would). 

If there are spelling and/or grammar mistakes sorry but i think i have covered them all, and thanks in advance to anyone who reply's to this. 

 

***EDIT***

Sorry forgot to say if anyone wants to ask questions on my current system or other questions on my uses for it please by all means go right ahead.

Do you have a particular budget and what are your current specs?

Current Specs are:

Processor - AMD Phenom II X6 1045T @3.48GHz

MB - ASUS Sabertooth 990FX/Gen3 R2.0 Motherboard

RAM - 16GB (4x4) GSkill Ripjaws Z Series 1866

Graphics/GPU - ASUS Nvidia GTX 550Ti

Primary Hard drive - 128GB Crucial SSD (forgot what model)

 

And as for budget i am looking for up to £300($480) on the high end but about £200-250($320-400) would be ideal. 

i found this: http://uk.pcpartpicker.com/p/1NsM2

its arround 250 pounds on Aria pc. Upgrading to a FX8350 could also be an good option later on.

How about an AMD 7930 or nVidia 670?

After a fair amount of research it has really high specs for the money, but i cannot find much about power consumption. I do not think it should be too much of a problem have a 650w PSU its just i have 7 hard drives to run with that too. Would power be a problem?

 

 And yes the FX8350 is something i am wanting to get in time. but for the moment what i have seems to work quite well 

I could not find anything relevant on the 7930 but the 670 is very pricey, compared to the suggested R9280x it looks over priced though i could be overlooking something :S 

280x is faster than any given Nvidia card that is sub-£300. You're fine with your 650W. Plenty of headroom.

Thank you for your help ^.^ 

mid range is always AMD 

Thank you ^.^