I copied this from Ultimate Guitar forum. Hope it'll help
"What amplifier do I need?
That depends on whether you want a valve or solid-state amp. That decision is a matter of nothing but personal taste, but its important as follows.
One of the differences between valve and SS amps is valves sound louder to the human ear (they aren?t actually any louder they just sound it).
As a rule we have for SS:
10-30W: practice on your own.
30-50W: practice with a band or recording.
50 to 100W (or more): Gigs (as much wattage as you ever need)
And for valves:
<20W: practice on your own
20-30W Band practice/Recording
>50W Hearing damage."