I'll echo the others. SVS, HSU or Onix/Rocket(AV123). All are very good subs and exceptional values.
Have owned HSU and currently am using the Onix UFW10. As with Mike, a personal favorite.
With trying to stereotype, the HSU and SVS are probably better suited to home theater. The Onix, toward music. Don't get me wrong, all of these subs handle both extremely well, it is just the SVS and HSU seem to dig a bit deeper, where the Onix seems to be a bit more musical. All this is to "my" ears.
As far as looks, I think the Onix is the winner here. A bit smaller and comes in some beautiful veneer finishes.
I'm sure your father will be more than pleased with any of the 3.
Regards,
Jeff