I'd go with the Randall over the Line6 being that those are your two choices.
I agree with everyone else about going with an all tube amp eventually though. Transistor amps have gotten way better these days, but they still haven't been able to get the warmth and depth of tone of a tube amp. The only drawback about a tube amp is that they require a bit more maintenance and care. For one, the tubes need to be replaced from time to time. In addition, the amp would have to be rebiased to ensure that the tubes and amp are being used to their best capacity. Also, the rule of thumb is that you have to make sure you check that your head is connected to speaker cabinet and that its impedance is compatible with the head, otherwise you could do some damage to the electronics and ruin the head.
Currently, my main amp is a Hughes & Kettner Tube 100 head with a Boss GT-8 effects unit controlling it. What attracted me to this amp, besides the tone and versatility was the fact that it's MIDI controllable, which means my effects unit can be used to switch the amp channels. It sure beats the hell out of tapdancing on effects pedals and a footswitch. I've had this thing since the early 90's and it's been faithful since day one. If If it died tomorrow, I'd probably look into (besides trying to source another one) an Engl Powerball or a Diezel amp. These amps are more of a high ticket item, but their tone and versatility is amazing. I've had Mesa Boogie Dual Rectifiers, Ampeg VL-100's and Marshall JCM-800 heads through the years. I sold them all because they were very one dimensional and "what you see is what you get". If you plan on playing with a single tone, they're great. Besides original bands, I was also playing in cover bands, so I needed something with a very wide range of tones.
