I am primarily a guitarist but I have been playing bass on the side in a cover band (classic rock and 80's metal) and I am looking to buy a relatively cheap bass for playing in bars. Does anyone have any experience with these basses or could recommend me something in the same price range?

Tell me what nation on this earth, was not born of tragedy-Primordial
due to me being a disgusting little fan boy, i'll point you in the direction of the rbx 374/5. i have heard very good things about the bb range as well.
I wouldn't call any BB models "cheap". They are mid grade instruments.

I am also not really a bass player, but I just bought a BB425x and it came last week in the mail (that is just the 5 string version). I really like it. American Musical Supply had a deal recently for $359 on this model if your purchased a red one. Regular price everywhere is between $600 and $650.

It has one tone and one volume. separate tone or volume knobs might be nice, but whatever. The low B string does not seem to buzz much and overall, it feels really nice. Again, I am not a bass player, but I have had a lot of fun with it.

Just FYI, the BB body shape is not very comfortable if you like to play sitting down. Lots of basses are that way I guess. I don't know much about the TRBX304 model.
Im also a Yamaha fan boy. Everyday i regret selling my trb and getting a dingwall instead.

There both brilliant bass's. I love the TRB shape and sounds so that would be my preference but all the BB's ive tried have been great. The TRB's are very versatile as well. I haven't played an x one though.
Yamaha TRB1006
Fender MIA jazz bass
Hora Hybrid double bass
Hartke lh 500
Ev 606L
Epiphone les paul