Hi Richard,
Are you wanting to upgrade for imaging purposes only? You could use your 130 SLT for that and invest in an 8" Dob for visual astronomy...? It really depends on your budget because there's some great imaging scopes out there but they cost big bikkies..
...I am by no means an imaging expert by the way, but if you want the best of both worlds, having a Dob and the SLT would be a great combo I reckon
