looking for suitable Mak for distant digiscoping

I know this is a bit OT here, but I need some advice for the following
situation:

I am trying to capture a family of Eagles from a distance of 500 feet or
slightly more. Due to the orientation of the nest and the height it is
located, I unfortunately can't get any closer. I have a C90 and I tried to
capture the family using a 14 mm wide angle eyepiece with afocal projection
into a digicam, but the results have been poor. I'm using a heavy duty
tripod and have shot a couple of hundred images at various focus settings,
both auto and manual but the images remain soft and fuzzy. I have been told
that I am pushing the magnification limits of the C90 and that is causing
the soft images. Some experiments from my backyard on stationary objects at
the same distance also seem to show the fuzziness. Conditions were a lot
more controlled. When I switched to a wider eyepiece of around 30 mm,
although images were brighter, there was still a degree of fuzziness. I
have suspected the C90 of being out of collimation, but the Christmas tree
ornament test shows it to be on.

The bottom line is that I really want to be able to capture this Eagle
family, as well as other birds at around the same range. How do I best do
this when 1) I can't get any closer and 2) I am on a limited budget and
can't spent a lot of money on equipment? I am considering an upgrade to an
ETX-125 or the Celestron equivalent, which appears to be on sale at this
time, but I don't know if the extra aperture will make a difference. Or,
maybe using a standard 6" reflector, which would be even cheaper and with a
mount, but I understand the mag can't be pushed as much as with Maks.

Any advice/ help would be greatly appreciated.

Thanks,
Jim