Try to steer away from 'spherical' mirrors. They are "quick & cheap to make by machine, & require no real hands on reworking to figure correctly" (Paraphrasing here from another IIS member's contribution, sorry I can't remember who). Spherical mirrors are used in scopes with a focal ratio greater than f/8, as the 'error' presented by such a shape is reduced, more mimicking a parabolic mirror. Should you use any really long focal length EP, or focal length reducing accessory, the image will be compromised.
Any good reflector worth its salt will have a parabolic mirror ( with a few exceptions ).
You can keep the GEM
and make a dob mount for it. The reason I recommend a dob mount is they are very easy to use, easier than an eq. mount (I'll dare anyone to disproove this,
, he says asking for trouble). If you are just starting out, I advocate dob mounts or alt-az mounts. Set-up time is bugger all, and less frustrating to use.
I have a SCT that has both a eq. mount & alt-az. I rarelly use its eq capability. I only set it up in eq. at star parties because I would use it to view the planets at high power, & its tracking motor makes it easy for novices to view, & 'NOT TOUCH THE BLOODY TELESCOPE', ( I really don't have anger management issues,
).
If the mount is woobly, then your enjoyment of it will match the wooble. Dob mounts also need to be stable, but if you make it yourself to overcome the shortcomings of the original mount, you really only gain. You WILL use your scope more. This equates to more cred. in convicing the other half that a more expensive new scope if worth it ( argue with that one,
).