I have a 50 watt JCM 800 and a Sentura II. I much prefer the Sentura II to the Marshall. I find the Marshall to be very bright, which is not what I'm looking for in either a guitar or bass amp. Cranked, it has that Marshall crunch, though.
The Sentura II (are you looking at a I or II?) has a lot of low end. I keep the bass control low to off in most cases. I like the mid boost. Not all models have it, as it was introduced later. With it on, I get a nice fat crunch, even at fairly low volume. Off, the amp is quite a bit brighter, perfect for early Stones stuff like Jumpin' Jack Flash.
