The archos does record PCM WAV at 16bit 48K.
You basically have 3 parts of your problem.
1. The mics. - Church Audio CA-14 are small, sound great and aren't too expensive, I'd get cardioids first, but the omnis are worth getting too. Sometimes Chris runs a special with a bundle.
2. Mic power/preamp - For rock music, a battery box should be sufficient, a preamp would provide mic power and add gain.
3. Recorder - Modern recorders record at 24bits instead of the 16 bits of the Archos. This is a very good thing as it means you get a 50% increase in the resolution when it comes to gain. more steps between quietest and loudest. This allows you to play conservative with your gain settings, knowing that you can't monitor or change settings while playing. As long as you end up with a peak volume between -12db and 0db on your recorder you have enough to make a very good 16 bit CD or MP3 recording. The Sony M10 is very popular on this board as it isn't too expensive ($220) has a very quiet, clean preamp and incredible battery life. At recommended settings you can record 4 hours on the onboard memory or add a MicroSD card and add up to 32gb more memory.