I'd recommend taking the Book 2 Epic as far as you can, and then also start the Book 3 Epic (in Rivendell). The Book 3 Epic will take you into Enedwaith where the quests will streamline you from 60-65 relatively quickly. It's also a more enjoyable zone than Mirkwood. You may have to go back and forth a bit b/w Mirkwood and Enedwaith depending on quest difficulty, but that would be best. However, this does depend on what quest packs you own if you are F2P versus VIP with Mirkwood expansion.
Once you get close to 65, you can keep going with the Epic story through Isengard - consider buying the ROI quest pack if you don't have the full expansion.
As for pre-ordering HD, I think you should wait until you you get through Riders of Rohan first. Yes, HD has upscaling so you can do the Big Battles, but until we learn what the effectiveness of upscaled characters is, whether or not you will gain EXP while being upscaled, and some other details, you may be best hoarding your money.
Krysfaerun (100 Minstrel), Wyrana (100 Guardian), Krysfrune (100 Rune-Keeper), Voxmoney (32 Warden), Merrykrysmas (38 Burglar) - Vox Immortalis
Krysbruin (61 Beorning) - Hammer of Wrath
Manlyman (41 Captain) - Tappa Kegga Dae