Hi Aidan,
Are those scopes F5 or F4?
you might want to see how big typical galaxies might be at that focal length using the ccd calculator.
http://www.newastro.com/book_new/camera_app.php
As mentioned, you ideally need longer focal length for galaxies as they're quite small, but longer FL's require much longer exposures.
Tradeoff is a 10inch F5 or 12inch F4. The 12inch is a lot bigger overall but should help with faint galaxies.
Are you imaging from dark skies? most galaxies are mag 9 or above with just a handful below that and they really require dark skies, else a light pollution filter. the IDAS LPS-P2 is a very good filter.
How are you guiding? an OAG saves you a lot of hassle with flexure but the spacing needs to be properly considered since you'll need a coma corrector as well.
F5 and below exhibit noticeable coma. the Baader MPCC mark 3 is a good choice. You'll need to maintain 55mm from the sensor to the Coma corrector and you just need the EOS to T2 adaptor.
The adaptor uses 10mm and the sensor to camera body is 45mm giving you 55mm.
if you're using an OAG, look at the teleskop express TS9OAG with an EOS adaptor on the camera side. that will help maintain the 55mm to the Coma corrector.
Finally, you will need a cheshire to collimate. you could start with a laser, but the cheshire is a lot more accurate and is the only tool you'll need to get it decently collimated.
Cheers
Alistair
