What is your budget, this is very important to carefully consider, you want to make sure you are getting the best value for money.
I currently have the Razer Taipan and it is the best mouse I have owned, I have had several over the last two years and I have to say that the build quality of the Tiapan is truly spectacular, it also suits my grip style (i use claw grip) perfectly. I have also had the Logitech G700 (had issues with the mouse shape in relation to my grip style, the mouse kind of forces you into a palm grip style, also the software was not quite up to scratch and the tracking could have been smoother) the Razer Mamba (served me very well and I would highly recommend this mouse the only possible drawback that I can think off is price) the Razer Lachesis (I bought this mouse mainly for the shape, which suited my grip style, it has all the features you would need in an fps fps game)
Software wise the Razer software suite Synapse 2.0 is also a great piece of software that allows you to really customize your mouse, most of the Razer mice supports synapse and the ones that dont have their own software which also serves the same function.
I firmly believe that the correct mouse for your grip style hand size etc. makes a huge differenced in your gaming performance, I would suggest taking as much time to research things like grip etc. etc. so that when it comes time to make that final purchasing decision you have all the facts and can make the best informed decision.
DPI comes down to personal preference, but most forums would suggest that for FPS games a DPI setting between 2600 and 3200 is ideal, personally I play on 2800 DPI on 1920x1080 resolution and have never felt the need to go beyond that, it really becomes difficult to keep tracking pinpoint smooth over 4000 DPI. Most pro gamers play around the 2600 DPI mark as well.
Here are some useful pages on mouse grip styles acceleration etc.
http://ravennestgames.blogspot.co.nz/2012/03/mouse-grips-and-which-mouse-suits-you.html
http://learningsc2.com/improving-your-play/disable-mouse-acceleration-windows-and-mac/
http://mybroadband.co.za/vb/showthread.php/491368-Best-gaming-mouse-currently-on-the-market?p=9512604#post9512604