Maybe you can take a look at the boss dr 202.
This is a drumcomputer with a bass synth.
It also got a 3 track seqencer.
For the drums, the bassline and a external device, sampler, synt etc etc.
It was my first machine, and i love him.

He has got real time control and fx.
And, it runs with batery's, so you can take him with you to the beach.
The price is about fl.850,-(400 us $)

Hope i helped you.