Refurbishing passive loudspeakers is an easy way to get your feet wet. For the 2400-2, I would recommend buying B&O Beovox (passive) S45-2s which are always for sale on Ebay.
Or if you're feeling like refurbing a pair, why not try these? The S40 is a wonderful speaker as well and easy to refoam and recap. I have both S45-2s and S40s (as well as 2 pairs of M70s) and you won't go wrong hooking a 2400-2 to either pair.
Check my M70 adoption thread under Vintage for more information (I did a comparison listen with either my BM 2400 or 1900), or my S40 refurb thread to see what you'd be getting yourself into fixing a pair of those.
Can't help you with the 5500.
Current primary listening: SMMC20EN -> BG4002 -> BM4000 -> Beovox M70