I've never understood this criticism of the akai's bass handling. I make dance remixes with thunderous bass with my S6000. And before that with 2 S1100's.
Don't worry about the bass, it's all there.
When I sample a bass heavy sound from cd, it sounds exactly the same when played back on the akai.
If money's an issue, go with the S5000, as you can always upgrade it to the same specs as the S6000. Although the removable front panel of the S6000 is totally sweet!
The A3000 is a good sampler too, the user interface is not as friendly as the 5000/6000 and it doesn't have the memory/polyphony potential as the Akai's... If your budget won't stretch to getting an Akai, do get the Yamaha (over the cheap EMU's or Roland's). But if you're ready for 128 voice polyphony and 256mb ram, native wav files, PC formatted hard disks, massive 3rd party sample cd support, killer filters and a huge graphic display..you'll beg/borrow/steal the extra cash for a new Akai. They're truely worth every penny.