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Hi Suzy, it seems you are learning fast.
First, I'll talk about eyepieces assuming you use your current dob, for which 5mm seems ideal for you for high power.
At high power,as you have realised, it's most likely you're looking at something small, on-axis, and a huge field of view is pointless assuming you can re-centre the object. What is more useful is the best image quality and contrast, on-axis.
it is for this reason many lunar and planetary observers are more interested in ep's with as few galss-air surfaces as possible, and would prefer MgF coatings (less scattered light when clean) to the broadband multicoatings (more durable but more scattered light).
The standout is the TMB supermonocentric (SMC) with just 2 glass-air surfaces.
From there its a toss-up between Brandons (best), Zeiss Abbe Orthoscopics (ZAO), Edmund RKE's (excellent bargain IMHO), or the run-of-the-mill ortho's which have 4 glass-air surfaces. Experienced planetary observers have some of these, if not a full set.
All of the widefield designs such as the GSO's, Vixen LVW's, Hyperions, Stratus', Naglers, Ethoi and the Pentax have many more glass-air surfaces and are all multicoated. Yes they give a lovely wide field, but look closely at a star or planet at high power and it's not such a beautiful view if you know what the textbooks say you should see with perfect optics.
Secondly there is the question of the focal ratio of your scope.
Trying to get good planetary images out of a typical f/5 dob is quite frankly fraught with the compromises associated with horribly short eyepieces.
If you want high power it is much better to start with a long focal length telescope (magnification = F/f, where F is the telescope focal length and f is the eyepiece focal length).
For example, for two scopes of the same aperture, one f/5 and the other at f/15, a 5mm eyepiece in the f/5 gives the same magnification as a 15mm in the f/15 scope. But the image quality will be chalk and cheese... an f/5 dob will have a huge secondary (degrades the image), and the 5mm eyepiece is a pain to use (never mind keep clean). An f/15 scope has a far smaller secondary (behaves like an APO refractor) and most 15mm eyepieces are quite comfortable to use.
Even better, almost all modern eyepieces work very well with an f/15 light cone, so there is really no need to splash out on the really expensive ones. On the other hand Brandons and orthos do not work well with scopes faster than f/7, usually they show some pretty horrendous aberrations over the outer third of the field of view.
It is for this reason I use an f/15 Mak, and a set of eyepieces that span 8 - 50mm...
* of the ones I mentioned, the Edmund RKE's were designed specifically for Newtonians at f/4,with respect to the curvature of the field and coma. For fast Newtonians these eyepieces are very much overlooked and they are startlingly good, for what they are.
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