Ibanez amps (in my opinion) are much worse than the Fenders or Marshalls that you are looking at.
Secondly...damn I wish I had a brother like you.
I personally have not played the Fender that you mention, but the Marshall Mg50 amps are really good deals for the price you pay.
I would go with the Mg50 if I were you...this amp should be big enough for club gigs etc, so he wont "outgrow" this amp too soon. I am also not sure what the Marshall AVT50 amps cost there ( In the States), but If you can afford one of those, your brother will be calling you "sir" for years to come.
[FONT=Century Gothic]Hope is when we feel the pain that makes us try again[/FONT]