Hi Stellarquest,
to IIS.
If you're prepared to wait, the 16" versions of the lightbridge and GSO will be coming out in the next 6 months - I think we'll see a flood of 2nd hand 8, 10 and 12" scopes on the buy/sell forum at good prices.
If you already have an 8", a step up to the 12" is definitely most recommended. There will be a difference between 8 and 10, but not as significant as the 8 to the 12. The 12" has some additional issues such as its size and weight, and longer cooldown time required because of the larger mirror, however the extra aperture and light gathering ability, and longer focal length, is (imo) worth the upgrade.