Speaker cone size has little to do with anything other than (perhaps) volume. Since studio monitors routinely use 8" and smaller LF drivers that continue down to 35Hz (and below), and have adequate power to drive them, there's really no excuse for the "listening with your eyes" mentality regarding speaker cone size.
I've been using a pair of KRK Rokit 8's for keys (Korg Kronos, PA3X), modeled guitar and bass in a relatively small practice room (maybe 10' x 12').
On the other end of the spectrum, I've got both a fEARless F112 and a fEARless F115 to handle about the same range at a much higher volume. Both of these cabinets are quite light for their output (34 lbs and 43.5 lbs), use neo-based drivers (12" / 15" Eminence Kappalite 3012LF and 3015LF low frequency drivers, respectively, plus a 5" Faital mids and a 1" tweeter). These cabinets are essentially PA-style cabinets with stunning bottom-end capabilities. The F115 will easily and accurately handle the low B on a five-string bass without farting out. The cabinet's got 98dB efficiency and will handle 900W. I'm driving them with either of two Carvin solid state stereo power amps of around 1500W (800W bridged/mono at 8 ohms, 1500W bridged/mono at 4 ohms --- both cabinets). Both weigh 9-10 lbs each.
The F112 sounds identical to the F115, but is a bit less efficient (due partly to the smaller cone size). But for most applications, it's more than enough punch and a treat to cart around due to the small size and weight. The larger cabinet and/or the pair of them together will put most birch ply bass rigs on the trailer. And they're both extremely clean with piano output.
The Altos (to me) just don't sound very good with piano, sorry, especially at volume. The QSC K12s I've used (with the subwoofer) do a decent job, but there's a reason that I've moved to the fEARless cabinets.
I've been using a pair of KRK Rokit 8's for keys (Korg Kronos, PA3X), modeled guitar and bass in a relatively small practice room (maybe 10' x 12').
On the other end of the spectrum, I've got both a fEARless F112 and a fEARless F115 to handle about the same range at a much higher volume. Both of these cabinets are quite light for their output (34 lbs and 43.5 lbs), use neo-based drivers (12" / 15" Eminence Kappalite 3012LF and 3015LF low frequency drivers, respectively, plus a 5" Faital mids and a 1" tweeter). These cabinets are essentially PA-style cabinets with stunning bottom-end capabilities. The F115 will easily and accurately handle the low B on a five-string bass without farting out. The cabinet's got 98dB efficiency and will handle 900W. I'm driving them with either of two Carvin solid state stereo power amps of around 1500W (800W bridged/mono at 8 ohms, 1500W bridged/mono at 4 ohms --- both cabinets). Both weigh 9-10 lbs each.
The F112 sounds identical to the F115, but is a bit less efficient (due partly to the smaller cone size). But for most applications, it's more than enough punch and a treat to cart around due to the small size and weight. The larger cabinet and/or the pair of them together will put most birch ply bass rigs on the trailer. And they're both extremely clean with piano output.
The Altos (to me) just don't sound very good with piano, sorry, especially at volume. The QSC K12s I've used (with the subwoofer) do a decent job, but there's a reason that I've moved to the fEARless cabinets.