The power supplies you mention only make sense for straight analog plug-ins. If you want to create a sampling 'scope front end, you need a vertical input *and* a special time base.
Devices like a 1S2 and a correctly configured 7S12 (for 7000-series mainframes) contain both. They are special-purpose devices because they are intended to be used in TDR applications. They contain/need a sampling head and a pulser.
Just adding a power supply to a sampling head, like an S-6, won't do. In order to use an S-6 you need a separate trigger facility as well, since it does not have a "trigger pickoff". The S-4 does.
A classic sampling system uses something like what is called "equivalent time sampling" in modern 'scopes: Samples are collected over many sweeps and the samples together produce the image, so no such thing as a fast one-shot acquisition.
A system like this only works with said (or equivalent) special time base.
In short: "I can stick a 1S2 into a 132 power supply and use the 1S2 with a Rigol scope" is not what it takes.
A general purpose sampling system (for the 7000 series, I'm not familiar with 500-family options) as a minimum consists of one 7S1 vertical input module, containing a sampling head like an S-6 or S-4, and a 7T11(A) time base. The 7S11 and 7T11 are connected directly (not via backplane only) to make things work.
Once you configure a sampling system like this, over 11 or even 14GHz bandwidth is your reward, not a meagre 1GHz or so.
Raymond
Froggie the Gremlin