Originally Posted by blackrobedone
I never did a side by side comparison but I owned both the 5150 II and the Peavey Ultra Plus. I believe they both sounded great, but they were very noisy. I had reliability issues with both of them. The Ultra Plus has more options (half power on the Ultra Plus 120, etc). I think they sound similar - beyond saturated, tear your face off tone, but a little mushy when cranked. I'd go with the Ultra Plus and pedals (as long as it's about $300-400 worth of pedals, and not 3 danelectros or behringers). Also, if the 5150 is in pristine, collector's condition, I'd keep it. Keep in mind the used values - 5150s can go for about $650-1000, and Ultra Plus about $300-500.
People pay $1000 for a 5150?!
You can get new 6505s for that. I'd say the range is closer to $500 to $800, with those going for $800 usually having a mod or two and some nice tubes. I bought my mint 5150 for $600 in the used section of Guitar Center.
The Ultra Plus wound up being the basis for the JSX, and it's a very solid amp on its own. While it doesn't have that "5150 sound" that's become so popular it's a great high gain amp, throw a boost in front and you can get some mean high gain tones that stay pretty tight. The cab will also be a big factor of course.