If I'm not mistaken, the XXL has upgraded servos over the LST2 - i.e. 2x JR 650's instead of the 590's.. So, they don't necessarily "suck"... 650's were an ideal upgrade for the LST2. They can also be had dirt cheap on ebay from chop shops.. Anything better is gonna cost a lot more.
BTW, FYI, Savox has a fantastic deal on servos now. Send in your old and get 20 bucks off.. I.e. you can get a 1258 for like $43 of something.... I just bought a Spektrum H6040, which is identical to the Savox 1258, for gas in DM-1, and it's wicked fast - plus 13 kilos...
https://www.savoxusa.com/SearchResults.asp?Cat=19