Andy
I've only been viewing for a few months, and in that time have tried to learn as much as I can about eyepieces.
I believe your priorities should be:
1. Buy (or make) a collimator and learn how to use it.
2. Buy a Telrad and star charts.
3. Buy a quality barlow such as an Orion Deluxe 2x ($100 for 1.25"; $200 for 2")
4. Depending on your viewing preferences, buy a 8mm TMB ($135) for planetary , and/or 13mm Orion Status ($199) for DSOs.
Unless your constantly trying to find perfection, all of these purchases should satisfy your viewing pleasure for many years. Obviously as you increase your viewing experiences, you will find what will be the best EPs to fill in the gaps, but your existing low power EPs will do for initially finding objects.
PS Keep watching the post in the Star Parties forum for parties at Cambroon. Great bunch of guys, and a wealth of knowledge. Not to mention a large collection of EPs which most are more than willing to let you try

.