Matt,
Saturn is a real challenge as it has very little contrast so don't expect too much apart from the major cloud bands. Can you see the Cassinni Division in the rings? If so you are not doing too bad especially as the rings are more side on this year. This is a good test of your seeing, mirror temperature and collimation.
If you are looking at a barlow I will go a bit against the normal advice given here and suggest that you get an apochromatic 1.25" 2x barlow like the Orion Shorty Plus or Celestron Ultima. Combine one of those with your selection of 1.25" lenses, especially the 15mm,and you have a great range.
Some points:
- Make sure your mirror is cooled to ambient.
- Use a fan on your mirror
- Collimate your scope as best you can
Planetary/luna observing is great but can be very frustrating at times.
Cheers