#1
Sorry but this might seem really stupid, anyway i was wondering whether Combo amps with speaker output's can be plugged into cabs?
#2
Isn't that the idea of a speaker output?
Basses:
Fender Precision Bass
Fender Jazz Bass
1967 Fender Coronado Bass II
Warwick Star Bass
Squier Precision Bass TB
#3
Yes...

If you're also going to run the internal speaker, then an impedence change is necessary and they usually have a switch to change the input impedence to match the resulting impedence with the external cab added.

Or they may just disconnect the internal speaker automatically when a cab is plugged into the speaker out jack.

There are a number of ways to do it. I had a B-52 AT212 combo (seperated into a head and cab now) that easily allowed the internal speakers to be unplugged if desired, giving two output jacks which run in parallel.
Benford Strat x 2
Burton Strat
Burton Tele
Malden Karma
Lawrence Tele
Squier Deluxe Strat

Valve Junior/Bitmo Modded
Bugera V55HD/412H-BK
#4
This sounds pretty sweet, now i just need to find a combo i like, probably the Bugera 6260.