These are all nice amps. The most clean will come from the 100 watters, but the 50 watters have more than enough clean headroom for most any user I have dealt with, and are generally the preferred wattage of any of the Marshall models for a more versitile amp.
None of the DSL or TSL amps sounds quite like the JCM 800.
The Randall is even more different than the other three amps but may have other aspects you find great.
This is a tough call, and it would be best for you to play all the amps and try to compare. Remember, if an amp cannot do a good clean sound, all it's other sounds will be compromised. would there be one that you would recommend more fot like metal and hard rock?