I had posted a similar thread a while ago
http://forum.audiogon.com/cgi-bin/fr.pl?aamps&1035511228&read&keyw&zzmv-55
I don't have a personal experience with the 11s, but from what I read, you will get more power and bass with the 6550, but you will loose the liquid midrange and highs of the EL34 out of the MV-55. Now if you are lucky, you might find a premier 11Xs which I believe are modified to accomodate EL34s. The solution I decided to go with to increase power was to ad a MF2250 to run the low end and anjoy the MV55 for the mids and hight (bi-wired configuration). great combo IMO. keep us posted of what you endup doing.
regards
shahen
http://forum.audiogon.com/cgi-bin/fr.pl?aamps&1035511228&read&keyw&zzmv-55
I don't have a personal experience with the 11s, but from what I read, you will get more power and bass with the 6550, but you will loose the liquid midrange and highs of the EL34 out of the MV-55. Now if you are lucky, you might find a premier 11Xs which I believe are modified to accomodate EL34s. The solution I decided to go with to increase power was to ad a MF2250 to run the low end and anjoy the MV55 for the mids and hight (bi-wired configuration). great combo IMO. keep us posted of what you endup doing.
regards
shahen