The Shiva is an awesome amp, but I'm not sure it will give him everything he wants. If he wants a blackface Fender and a hot rodded Marshall, the Shiva will fit him like a glove, but I'm not sure that's what he wants (not really made for that jangly Vox Beatles tone at all - doesn't really have that mid and upper frequency push and emphasis).
Line 6 does have solid representations of amps and if you want a cheap alternative to getting similar tones, that's probably the best way to go.
I agree with the earlier post about EL-84s. They are the only power tubes I know of that can get that chimey, mid oriented clean tone and still do straight up rock and roll right. That's what my Fargen has (as do many other amps like Vox). They just might be my favorite kind of tube.