I bought a Vox AC4TV combo and it's been 3 months and is played 7 to 8 hours every week. In the 4W mode, the clean sounds great as expected at low volume. But when the volume goes past noon, it starts to break up, but the break up is not too pleasant/smooth/warm. On the other hand, in the 1 and 1/4 W modes, the breakup is sweet like marshall crunch to some extent. It has a cheap Celestion 10 inch speaker and I use ibanez rg570. Any thoughts of what might be the problem in 4W mode?