In general, straight SBDs are a mistake. They are mixed for house sound (to sound good in the room), not to sound good as a standalone recording. Guitar amps are often not mic'd at all and therefore don't go through the board, or will be much much lower in the mix. Sometimes an SBD will be all vox and drums.
These budgets highlight the fact that it's tough to really get a great sounding set of mics AND multi-channel capability, since the multi-channel decks generally used here still run north of $500. But, if you don't make that a priority, there are tons of great sounding mics that pair nicely with a naiant littlebox, which can run into your M10.
$250 - stick with what you have (the CA11 and M10). If you are really set on trying 4-channel with SBDs, get a Tascam DR2D for $200. Folks elsewhere on here have explained how to do a 4-track recording with it, though it is not as easy as with a bigger 4-channel deck. You can run the CA11 and a board feed though you will probably need some attenuator cables for the board feed.
$500 - I'd probably upgrade to open taping mics and a preamp. You can get some Studio Projects C4s or Nak300s for $200 and a Naiant littlebox for about $250 and run that into the M10. You'd need to spend the rest on a stand and mounts and cables which will put you a little past $500. Or, get a DR2D ($200) and upgrade your CA-11s to some CA-14s ($150?)
$750 - if you're still mostly obsessed with doing SBDs, get a used Edirol R-44 or a Tascam DR-680 and run the CA11s and a board feed into that. If not, I'd probably say get some Busman BSC1 mics ($500 new) or a comparable set of good used mics and the naiant littlebox and run that into the M10. Again, with cables and a stand added in you'd be slightly over budget unless you buy used. If it were me, I'd do the latter.
$1000 - same deal. At this level you can afford either a new multichannel deck and some very inexpensive mics (i.e., Tascam DR680+Studio Project C4s used comes to about $1000) or a pretty nice rig with some used mics. I'd probably say get some better used mics and littlebox and run that into the M10 still. Things you could probably afford would be Peluso CEMC6, used AKG 460s, used AKG 391s, etc. There are some 391s in the Yard Sale still today, and I think some 460s maybe too.
I'd probably get a nice open-taping stereo rig, and then if you want to play around with SBD, just get something really cheap like a used iRiver or even one of the very basic new SD recorders for around $100.