If you are moving up from a Holga almost anything will blow your socks off optically. If you are insistent about the TTL, then I would go with the Bronicas or a souped up Kiev, though you need to recognize that the meters on the latter are not coupled to the shutters, so using the meter doesn't speed work much, if at all. Someone else can tell you whether this is an issue for the Bronicas. I never used the meter on my Kiev 60, and didn't even bother to get one on my Arax.
Before makig that kind of investment, I would suggest trying an older folder and an old TLR to see which method of composition you prefer. Then move on to a rangefinder, better TLR, or SLR as suits you. There is more advice than you can digest on Robert Monaghan's web site Dead Link Removed. For TLRs, it is hard to go wrong with the Ciroflexes, Yashicas, Flexarets, 'cords, and many others in the under $100 range. Seems everyone but Nikon and Canon made a TLR in the 50s - Monaghan shows a list from Modern Photography in 1956 of 32 models from 5 countris . The choices in folders are almost endless, but the two Russian Zeiss copies, the Moskva and the Iskra, offer good value for the price, with good optics and couple rangefinders, though somewhat shoddy cosmetics. Note: the Moskva is left handed, so that may be an issue.
Be forewarned, the old folders can be seductive. They look beautiful and people will walk up to you on the street and ask about them (to a lesser degree this is true of TLRs as well - and old press and field cameras will actually attract groups). You may develop a lust for the old folders and their soft leather and bright chrome - but I digress.