Although you can physically plug more than one USB interface at one time into your laptop, I wouldn't do it. The Tascam 1800 has enough trouble keeping glitch-free transfers going without competing with another one of itself. Added to which, it's doubtful that your DAW would recognise more than one USB audio device at a time.

Does your latop have a Cardbus or other slot? If so, I would consider getting a plug-in FireWire card (make sure it has a TI chipset), and then you have a much wider choice of multi-channel interfaces, many of which will daisy-chain at the FireWire level and appear as a single larger interface to the software.

Thnaks Boswell. No it is quite limited for expansion with only having 3 usb ports. It is fine for running reason, but now I have joined a Band we would like to do some live and reheasal recording with a bit more control than just a mic. I could sub mix the the drums it wont be too bad using just one Tascam them.

Are you set on the Tascam 1800, then? I wish I were more enthusiastic about it for recording drums. You need good headroom, and Tascam interfaces are not renowned for that.

You could plug a second 4-channel pre-amp into the Tascam's line inputs to get you 12 mic channels in total. If you chose well for the external pre-amp, you could put the kick, snare and overheads through that and you would get a better result than taking those mics straight into the 1800, and a great deal better than attempting a live mix-down to 2 or 4 channels to free up others for the rest of the band.

What's your budget for new hardware?