I had been trying for a couple of years to get guitar and vocals together through the Marlin amplifier, using a couple of very cheap mixers bought from Maplin. This didn't really work as those mixers didn't have any preamp for microphone input. I realised this year that what I needed was a proper mixer, and in April I purchased the Behringer from Studiospares.
This has been one of my best ever purchases. It has 12 inputs - four mic-level and four stereo line-level - and allows me to plug my guitars, keyboards and microphone all in together. It has an impressive array of onboard effects - including reverb and delay - which do wonders for my vocals! It doesn't have USB - my intention was performance rather than recording with this mixer, but I can feed the output into the line in socket of the PC and capture the audio using software such as Audacity. The great thing is that is everything is permanently set up so that I can switch on at any time and play and sing when the mood takes me. The Behringer has given me my "music corner", which is the closest I will get to a rehearsal or recording studio with my limited space.
My only reservation about the Behringer is the power supply. It is connected to the mixer via a DIN plug with very flimsy pins. I'm very wary of disconnecting the power lead as I'm not confident that I'd be able to plug it in again without breaking the pins!