I agree with the other guys that have replied. A Fender Twin is a great amp for clean tone at higher volume. However, be aware that it is a tube amp and will sound different that your Fender chorus which is solid state. But I have prefer the sound of tubes. Silver faced Twins from the late '70's
can be found for $500-$800, depending on the condition. The main thing to look for is, the age of the tubes and look for original speakers. Also be prepared to spend some bucks have the amp checked out. Tube amps require more care that solid state amps. My
advice is to have the filter capcitors checked and replaced as needed(if a filter cap goes,it can take the whole amp with it). Check the power and output transformers make sure the tube sockets are tight and the power
tubes are not too old(while playing through amp check to see if power tubes turn from orange to a blue glow, if they do it's time to replace them). DO NOT DO NOT use GROOVE Tubes as your replacements if you plan to use the amp for a clean sound. They tend to be hotter than other brands and will offer more break up or distortion. RUBY TUBES are a great all around replacement tube and less expensive. Other good amps to use for a clean sound are Fender Vibrasonics. The first generation from '60-63 are brown faced and are rare and expensive. Fender started making these amps again in the '70s for use with steel guitar. They have the same basic tube configuation as Twins, but also offer a vibrato circuit.
Fender Bandmaster heads and
Concert Pros will also give you a clean tone at higher volume. Just keep in mind that these amps have chorus built in.....here is the solution. Slave your Princeton with whatever louder amp you eventualy buy. Plug your guitar into your Princeton set it to a very low volume then run a cable from the second input jack on it to the input jack on your new amp. Now adjust the volume and EQ on both amps to achieve the tone that you like. Also try doing this with your Marshall
after it's out of the shop BEFORE INVESTING into another amp unless you are itching for some new gear.........have fun.