AR-15 recommendations?

[MT2008]

I talked to my Dad today, and he's finally proving receptive to something I've suggested for a long time: Buying an AR-15. We're looking to buy an M4 look-a-like, and I'm trying to figure out the options available. In terms of guns that are close M4gerys, I'm aware of:

-Colt Law Enforcement Carbine

-Bushmaster M4A3

-DPMS AP4 Panther

-Olympic Arms K3B-M4

The Colt is probably not going to be an option, due to the cost. I was thinking about buying an Olympic Arms lower and maybe finding an M4-style upper, but what does everyone think? Anyone got suggestions?

(BTW: I also kind of like the OlyArms Plinker Plus 20, only because it looks so much like the M16s that the Canadian armorers use.)