Hi,

A psedo differential amp basically does not have a bottom current source. Is this correct?

If I am correct, then it should not really affect your gain-BW-power trade-off. It will affect only your output swing and CMRR. If you have some kind of fast settling CMFB (common-mode feedback), then I think you can have "reasonable" CMRR and get away without problems in your pseudo differential amplifier.

Hope this helps.
-Sid