i mention the GT2 and JD10 for this reason:
usually i use them direct in a mixer, and very happily so. i'm pretty sure they would sound good into a decent hifi too.
but i was practising with a friend, and he unfortunately had just some sort of 15w solid state combo which was rather grungey sounding.
i set it to a clean setting, and used my SansAmp GT2 for distortion. it actually sounded decent - ok not up to my JMP50 - but significantly nicer than the drive on the combo itself. due to the small speaker, the tone was missing some low end... hardly an issue for practise.
if i needed to have a practise combo on a budget, i decided thats what i'd do.
never tried a JD10, but i plan to just as a variation to the gt2. gt2 sounds quite nice driving the jmp50, as long as the jmp is set to totally clean. quite funny to use the mesa-boogie 'model' in this way.
i'm sure a line6 pod or whatever would have more features. but i like the simplicity and non-digitalness of the GT2, it has its own character, and a robust stompbox format. i'm completely confident the JD10 would be cool too due to its reputation.