I have had both the f7 and the xa25. they sound very different. have you heard them because the sound is important. after getting the xa25 I sold the f7 because I never listened to it. the xa25 is that much better to my ears than the f7. As a side note they are hot. the xa25 is like 4 60 watt light bulbs being on so it needs some room to disperse the heat but it is one of the best amps I ever heard and owned.
JH