An 8" f6 is exactly the same focal length as a 6" f8, just a little larger in diameter. If you can handle the 6, then the 8 will be manageable and much easier to just 'plonk' outside and be observing in minutes (planets will of course require mirror cooling). If you go with the 10" then perhaps the truss or semi truss is better from a weight point of view. The truss 'scopes do take longer to set-up and yes collimation should be checked and is often needed. You will also need a shroud of course. Note too that shiny aluminium truss poles will affect contrast.
The 8" will give you 1.78x the light gathering power over a 6" wheareas a 10" will give 2.78x over a 6". A good upgrade path is 6" - 10" - 16" with each jump giving over 2.5x a brightness increase. Another good upgrade path is 8" - 12" - 18" with each brightness jump being 2.25x.
You will notice a difference between your 6" and 8" particularly on globulars as you will be able to resolve more and the stars within the globular will be brighter. Planets will appear similar but the resolution gain can be detected in good seeing. The brightness gain is important on planets mainly at the high power end where you will get a larger exit pupil at the higher powers.
If you are set on an 8" then I would go with an 8" tube for general use at home or a trip to a dark sky and would only consider an 8" truss if I was travelling. Otherwise consider a 10" truss or semi truss design.
Note you can get a hand trolley and strap the dob base and tube to it with luggage straps to make it easier to move around. Get one with large pneumatic tyres rather than solid tyres to take the bumps better. This would work well with an 8" or 10" tube telescope.
If you have aperture fever then going from a 6" to 8" may be like taking one paracetamol when you should have taken two; the fever may go away but could just as likely come back with a vengeance.
Whatever you choose, enjoy!
Note on f ratio: Your 6" is f8 and an 8" will likely be f6. A 10" will likely be f5 and will show more noticeable coma and also require premium eyepieces to perform well. You may even need a Paracorr at f5 if coma bothers you.