The SR-16 is a nice drum machine. I used to own one.
If your primary goal is to have something to jam with there may be better choices out there. For instance the digitech RP
series of pedals have 30 drum loops
built in. I think the rp80 is about $80. There are also some very cool devices like the Boss Jamstation.
I have "Band in a Box" on the computer and it is a blast. The only problem is that it is not portable.