Now we have one question answered, there's a post on Youtube with a comparison of two V5's: one stock and one with a Celestion G-10 speaker on it.
On a side by side camparison you can tell that a speaker change helps a lot.

Video is posted by The Tone King... great reviews from him.
http://www.youtube.com/watch?v=na0mrc1QZoY

Take a look and tell me (us) what you think now that you can be able to listen to a stock V5.

Oops, +-100 bucks for a G10 speaker... ouch.
Any recomendations on a good not-so-expensive 10" speaker?