Suzy,
if you can manage it, I would recommend upgrading to a 10" rather than an 8". An 8" seems like too much of an incremental upgrade. Go for the maximum aperture that you can handle / afford. There may be ways that you can handle a 10" without having to lift it here and there, depending on where you observe from vs where you store your scope. For example, as Astro mentioned, you may be able to use a hand trolley to move a 10" scope around. Alternatively, perhaps a set of handles with wheels might do the trick so that you could wheel the fully assembled scope around sort of like a wheel barrow.
In the case of my 10" LX200GPS - I find it too heavy to move around / assemble etc, so I have it permanently mounted on a custom wheely bar sort of set up with leveling bolts - so I just wheel the fully assembled scope to my observing pad, level it, and I'm off and running with zero effort. If I had to carry that scope and mount it on the wedge every time I wanted to observe, I think I'd end up selling it for something more convenient.
I've used tube dobs and truss dobs and have liked them both. I had a 10" f/6 tube dob for years and absolutely loved it. I think that 10" is the sweet spot before you really start getting into heavy / less convenient scopes. I'm a firm believer that the more convenient a scope is to use, the more it will be used.
My 15" truss dob was a little more trouble to move around and quite heavy. However, the views more than made up for the inconvenience. I made a set of handles with wheels for the rocker box of the 15" but could never bring myself to drill the female threaded sockets into the cabinet
So, those handles were never used even though it meant that I could have left the 15" fully assembled at all times and cut the fuss down to almost zero. I guess the point here is that there was a way of increasing the convenience of using that scope that would have been perfect (if I wasn't so scared of drilling holes in an obsession).
I'm sure you'll end up with just the right scope for your needs regardless Suzy. If you think a larger scope would be better, I'm absolutely sure that there'll be a way for you to increase the convenience / ease of moving it and setting it up.
Dean