>> I'd like a 3U (3U x 84hp for example) since I am limited in what I can purchase.

There used to be a case called the G3 which is exactly what you want, however, possibly it was discontinued, as the price was almost the same as the G6 (the 6u version of the same)

The G3 may still be available, but, if not, someone may have one 2nd hand

Julian