I used a Fostex FD-8 for years with an Alesis 32 in front of it. I'm assuming you want to be able to do a submix of say 4 mics or so, so you can mic live drums or several amps at once or something.
Though Mackie is not a favorite around here, you can probably pick up a used 1202 for cheap (look for $100-$150), and it'll do fine for a little project thing. Or you can look at the Soudcraft Spirits for a bit more. There's lots of cheap boards to be found. The only thing is the MR8 needs to have two inputs you can pan left and right (assuming you want a stereo 2-channel submix), so you can take your stereo mix out of whatever board you end up with. (You could also do this mono to just one track on the MR8.)
I know it has two XLR inputs, but it'd be better not to go into those, since your mics will already be using the pres on the board, and using the XLR mic inputs on the MR8 would run them through a second set of pres. From what I see on the MR8 literature, it has 2 "guitar" inputs. These will probably work. Just go your stereo mix out from the board and then into those and pan the two tracks hard left and right.
I'm not an expert and maybe someone here can give further advice, but I know that using an external board like this with a Fostex unit served me well. You get better EQs, and auxilliarys if you want to use effects. You can even take it a step further like I did and buy the Fostex digital to analog converter ($250 new), which lets you take the lightpipe out of your MR8 and covert to 8 analog tracks to feed to the board. So when you mixdown, you can do it on the board with better EQ and more auxillarys. You'd also be able to record up to 8 tracks at once that way.
the D/A converter is called
the Fostex VC-8. In this case the MR8 becomes simply a recorder and everything's being done through the board.