Hard to say. I have 4130 and I love it but all the reviews say that it runs hotter and is less power efficient than the vishera line of CPU's I think in the long run you will be happier and better served with fx 6300 if you can afford the extra 20 bucks.. If you haven't already looked check out:
http://www.tomshardware.com/reviews/gaming-cpu-review-overclock,3106-5.html
In the end I think it comes down to what price point your trying to keep it at and what exactly you want to do with your new computer.. If you don't rip or edit huge video files or run massive applications you wont need those extra cores for another year or so. a matched kit of ram on four cores will still smoke any single thread application so In my case I went with the l3 cache on the FX series CPUs .. Im not sure if theres a " Best Answer " without knowing what your wanting to do with your new computer. Some people will tell you what you they did with their money and some people will tell you what they would do with your money lol but in the end I recommend this.
If you want a gaming rig you can upgrade later on go with the FX / am3+ cpu/motherboard
If you don't need the extra cores on the 6300 spend the money you save on a better graphics card or ram
If you don't have any extra money you can sacrifice a core , go with the Athlon II X3 ( which there is a 25% chance you get a unlockable stable 4th core Phenom II)
hope I've been able to help. BTW I picked the fx 4130 (95$) with the ECS M960-M3 (45$) for my budget gaming rig.
hope this has helped you and not confused you.