Speaker "Tune Up"? / Speaker alternatives

[Zap]

I'm happily listening to my system at the moment, but I was curious if something should be done for the speakers since they are around 40 years old.

I've got a pair of Telefunken 3-way RB 46 speakers and I was curious at their age if the crossover capacitors are still going to be very good, or if it would be suggested that they be replaced. I haven't had the speakers for very long, so obviously I can't vouch for changing sound over the years. They sound really good, but I wouldn't be surprised if they could sound even better.

The second question is if there is a reliable way to SAFELY determine the polarity since the leads aren't marked for some reason. I am pretty sure I have both speakers hooked up right, as the sound is the most accurate this way. The grille is permanently attached so I can't see the speakers easily.

Finally, I was curious if anyone would have suggestions for a DIY speaker project that would specifically OUT DO these speakers. They are supposedly Teak wood cabinets, seem to have really good high frequency repsonse, have a decent efficiency (91-93 dB approx?).

I was told they are only a so-so speaker, and if that is the case I want to hear a set of really good speakers!! I've read some of the links posted in the past regarding DIY designs, but it seems like many of them don't have that great of an efficiency rating. I'd eventually like to build a SE 45 amp and see what the fuss is all about, so an efficient set of speakers is desirable.

Thanks