Let me elaborate on my response just two posts above, as I have been facing a similar dilemma from the opposite side: owning a Spendor (BC-1) and deciding whether to buy something else.
If your original selection was good, then relative to other newer offerings in the market, your speakers' dollar value will depreciate far more than their sonic qualities. You can spend a lot of money and end up with no sonic improvement or very little improvement. I know that my speakers are not the best in the world, but they are so good to my ears that a meaningful improvement would have cost much more than what I was prepared to spend.
Two caveats to this: First, if after careful audioning you really like something and can afford the difference, by all means go for it. Second, for experimenting around when you are not sure, buying used eases the pain a little. If you buy carefully, you can usually sell them for no loss, although shipping such heavy speakers back and forth is not something I look forward to (but YMMV).
So if you feel like experimenting, a used "SP-100 R" is listed at A'gon (I have no connection with that sale). If the price is agreeable, go ahead and try them - and please remember to post your findings here. :)
