Hi Gerry.
I'm not an expert by any definition but I will make a few suggestions based on my experience.
I have a Skywatcher Equinox 120 f7.5 scope which works VERY well with the Quark. I think the SW120ED is f8.3 so should also work well.
The 90mm f7 Stellarvue should also suit the Quark pretty well although you will probably want to use a x0.5 reducer on the camera with both scopes for imaging.
I use a cheap 0.25" one from Ascension - not sure where in the world you are (would help to know for people giving advice) but this link to a UK dealer will give you an idea :
http://www.telescopehouse.com/acatalog/ ... 1.25-.html
I produce 6-pane full disc mosaics with the Quark, Equinox 80 and x0.5 reducer - not as easy as using a small scope (like my SM40) but not that hard. I'm not sure that an additional small scope just for full discs makes sense - will probably be of limited use in a year or two as the sun quietens down whereas there will still be lots to see in high res.
Re your mount, it depends on what you want to do. It is certainly easier to image if you have a permanently mounted equatorial mount (as I do) but it is perfectly possible to get good results with an alt az. I have an iOptron Mini Tower goto alt/az which I use as a grab and go or travelling mount with my Equinox 80 or SM40 solar scope and it is great for 'casual' imaging sessions. The main problem with an alt/az is that you get image rotation as the object is tracked which makes capturing/processing time-lapse sequences very difficult. I use a Skywatcher HEQ5Pro mount on a pier and controlled via EQMod which does make life pretty easy as I can be set up and imaging within 5 minutes
Loads of people on here will give you advice on cameras and all have their favourites
I think that there are 3 main manufacturers (and several minor ones - depends on where you are).
1. Imaging Source DMK: good planetary/lunar cameras also widely used for solar work. Some love them, some like them, very few hate them
DMK21 is 640x480 pixels - ideal for planets but a bit limiting for the sun in my opinion but some use it to good effect.
DMK41 is 1280x960 - I find this a very good size and used it for solar imaging for several years.
DMK31 is roughly half way between the above - Mark Townley gets great results from his with his Quark and ED80.
DMK51 is bigger but has a slower frame rate (always a trade off - see below).
2.ZWO cameras have been around for a couple of years and have a pretty good reputation. I had the original ZWOASI120MM which was excellent for planets, lunar and white light sun but drove me mad with Newton's rings when used for Ha. They have just released a new camera - ZWOASI174 - several people on here have just got one and most seem very happy. It is probably what I would get if I was looking for a new camera.
3. Point Grey cameras are very expensive but, until very recently, were probably the best available. I use the Grasshopper 3 along with several other people on here but the expense and their reputation for being demanding and fussy about computers (they are NOT designed for amateur astronomy use) put lots of people off.
Things to consider with cameras include:
Sensor size: bigger is nice but more expensive and more demanding on computer power. More pixels 'tend' to mean slower frame rate - eg DMK21 = 640x480 at 60fps, DMK41 = 1280x960 at 15fps (same amount of data per second)
Sensor type: ccd has long been better (no Newton's rings - more sensitive) than cmos or cmosis BUT this is changing - see the ZWOASI174
Frame rate: more frames in a shorter time is useful if (like me) your seeing is usually poor but is much less important if you have good seeing most days.
Computer interface: USB3 is faster than USB2 and some/most people prefer it to firewire or gige connections which need extra gear and can be tricky.
Processing software once again comes in 3 main packages - good news is that they are all free
I use AutoStakkert for most of my processing (followed by tweaking in Photoshop) but also use Registax and AviStack from time to time. Different people will tell you that their choice is best but.................. they all work well and its mainly just which appeals to your work-flow.
OK, I think that's enough to get you thinking and researching
Just bear in mind that these are just my views - others will agree/disagree/laugh at etc.
Good luck and look forward to hearing how you get on.