Possible broken Vox Valvetronix Amp 40+W, need advice

So when I went to go play guitar today as usual and I turned on my amp I noticed there was no sound coming out. After turning it off for a while and then turning it back on, it worked but only for the sound to fade seconds later. I called a guitar tech at a local shop and he said it could possibly be the tube blew out but to fix it would cost almost as much as the amp itself. It's either this or the 9V battery for the pickups in my guitar is dead. In that case, that would be a couple dollar fix. However, if I find out for sure this Vox is bricked what amps would you guys recommend that have a good distortion sound? I'm considering a Mesa Rectoverb 50. They have a couple used ones at guitar center for around $500. Does this sound like a good investment to get an upgrade or should I seek something better priced? Thanks for your guys' help, this has been a real inconvenience.