I think you could probably find some examples of those Morris boats within your price range, and from what I've seen they tend to be well-equipped, maintained, upgraded, etc. Maybe worth another look. And, yes, I was referring to the CS36T, I think the Merlins are newer and pricier.
As for the boats you are currently focussing on, I have been aboard (but not sailed) the Shannon 28 and Orion 27, as well as a CD 33.
We looked at a few Orions before we bought our current boat. I really like them. But my wife thought they felt cramped compared to our then Dana 24. Obviously, the Orion IS larger, but the open interior of the Dana (and our current 31) gives the feeling of a roomier boat.
If you end-up focussing on the Orion, I would suggest you look for a Mark II version if possible, as they have a longer coachroof and an extra set of portlights -- all nice. Of course, you also have to decide which interior you prefer (A or C layout) -- I like the sit-down nav station, personally, but they both have their respective merits.
The Shannon 28 is a neat boat -- it has an open interior and layout similar to what we had in the Dana, only in a larger platform with a cruising fin keel and transom/skeg hung rudder. This boat felt like a Dana on steroids when I was aboard. I liked it a lot, but we needed a quarter berth which it lacked.
The CD 33 is typical Carl Alberg -- fairly narrow for its length by todays standards. I have a soft spot for CDs in general, but the one I really like is the CD 30 Mark II, which was a later design by Clive Dent. It is much beamier than the Alberg designs, and has a nice layout in my opinion. Here's an example: CD 30 Mark II
Hope this helps!