I've had both big block (ERA427SC) and small block (FIA) ERAs. If you stick with a 428 and don't go crazy (ie; Webers, etc.) $10k is reasonable number for the 428 motor and it will have more than enough power and sound great on the street. 427s tend to have a slightly harsher tone.
On the other hand, I have a Dart 302 (b/s to 347ci) with Dart aluminum heads zero balance forged crank, Webers, etc. in my FIA and have somewhere between $15-20k in that motor.
So, a lot depends upon your ability to restrain your motormania...
See:
Jim's USRRC
(The motor in the car in the pictures has Gurney Eagle heads which has gone in to an ERAGT. I have since replaced it with the Dart motor in the FIA)
Jim