(1) goto gta forum and see configs of people who can run maxed out. What CPU, what graphics card, how much memory, etc.
(2) decide if you want to build or buy (or a hybrid of the two -- buy CPU and upgrade video)
(3) If you decide to buy then google to find brands of gaming systems that match your spec from step 1 above. For example, is there a cyberpower PC that works? google cyberpower. there are many makers of prebuilt gaming systems.
$1100 should get you a monster. Avoid AMD at all costs for CPU -- they are currently just not competitive. An intel i5 (e.g. i5-2400) should be the processor for an $1100 system. Video should be around $400. Rest is quality case, power supply, MB, memory, disks, etc.