I would suggest going for the Athlon ii and the GT440 build.That build is more powerful than the A4-3400 and you have the option of upgrading down the road since the Athlon use's the AM3 socket.The GT440 is also much more powerful than the A4-3400(6450).
Can you list your full build parts for the Athlon build?
Herr_Koos is right!
First you must make a decision:
a) Multimedia machine - HTPC + some web browsing or
b) game machine.
The philosophy of the machines is totaly different!
For HTPC you should have SPDIF, HDMI, 2GB not more, Blue ray player, AMD A4 or A6 is great and "future proof" + LCD/LED TV and great audio system for total leasure.
Actualy, my home HTPC is made of A4 x3AMD (65W) + 2x500GB + wireless A4tech Mouse + keyboard + 42" LCD Philips +LG DVD playe+ LG Harmony 300 remote (for controling the PC, TV, LG player and the Digital Receiver). The HTPC is connected to my Linksys 160N router.
For a) A4 i the option. Using a less power, less noise, less hardware, less space, less cables and etc. 2GB is what you need. UBUNTU as OS and you are ready to have a fun
b) Game machine... then you need something much stronger! For games, choose i5 and min. HD5770, min 4GB ram...
This machine is quite old but it's good for now: intel Q6600 + AMD HD5770, 6GB Ram, 2x500GB HDD, 23" ASUS monitor, ... and i'm using for rendering, drawing and casual gaming.
For those types of games either system will do but you might want to go with the Athlon just for upgrade sake.Unless AMD is planning to release some new CPU's that will work for the FM1 socket with Piledriver.