for a 303 sound the best hardware equivelant is the future anaolg technologies (FAT) fb383. its a 1u rack mount 303 clone, it has all the same circuits inside but no sequencer, its midi controlled. i have one of each and find there to be no difference, its that good. you miss out on the fun of the roland sequencer but if you have a tr909 you can run it as and external instrument from it.
there is a mark 2 version which has a slide switch ( the first one you had to play portamento to get a slide) which makes this the one to get.
the company had a name change though and are now called MAM ( music and more) and are german. its still called the fb383 though. you should look out for them second hand as they are pretty cheap used.
as for drum machines,
the roland tr909 is still the man when it comes to drum machines.
the novation drumstation is a clone of the 909 and 808 and sounds pretty close although nothing beats the real thing and again its midi controlled, no sequencer. i have all three as i aint rich enough to own doubles of the 909 and 808 so the drumstation covers fine for when i need it.
a good sampler can cover a lot of instruments in the studio though and may be worth considering, it can be a drum module, a synth, anything.
if you want 303 sounds, i would avoid trying to get a synth that can make similar sounds as one if its patches. its always a much better sound if you can get something designed specifically to do the job you want rather than making do or coming close.
good luck
