Should I buy a new amplifier; and if so, what?

Look in to a Krell FPB 400cx. It's a nice sounding amp.

I always find it interesting the fault protection on expensive amplifiers, there is none apparently. So now you're presented with $6000 repair bill just to get back to square one, no improvement or spend more money on a new amp. If you're left with those choices I would buy a new amp every 5 years just to be safe it might actually save you some money in the long run.

Classe?

The Levinson 336 is a 10k amp. The reason Levinson repair center charges 3000 dollars is brutal. This is how they make a huge profit. The 336 when the caps explode it will take out the 3 surge resistors on the slow start circuit. you can replace those wires very cheap. These surge resistors are there to protect the amp in case there's a short or capacitor fail. No other high end amps have this cap problem. The reason they used philips caps made in China. They used these caps on 331/332/333/334/335/336 and Levinson 33h. These caps need to be changed on these amps. You can replace these caps for 800 dollars on 336. These caps are very hard to find. I have purchased caps for all these amps from factory. Very expensive. Because no one uses this high voltage for filter supply.

The problem is..older amps use large single caps for plus and minus rail voltages. They take up a lot of space as well. Newer amps use many small caps in parallel to make up the large capacitance. The advantage besides size requirements is, small caps have less ESR (equivalent series resistance). This allows the smaller caps to rapidly deliver their current under transient conditions and recover quicker, which in turn makes the amp sound 'fast'. This is especially true in the bottom end i.e. slam.