Ohm Walsh 4 conundrum.

I'm new here and the main reason I joined is it appears there's lots of Ohm speaker owners at Audiogon. A little background first.  I've owned my 4's since 1986 they were a store demo that were built in 1984. They were refoamed in 1998 by Ohm.  They're driven by a Nakamichi PA-7A MKII amp and CA-7A preamp, TT is a Heybrook tt2 with Linn LVX arm and AT- OC9 ML cart, CD is a Yamaha CD-C600.  The amp and preamp are currently being checked out by a tech who used to do the warranty work for Nakamichi when they were still alive and well.  I'm almost 72 years old and I've noticed a distinct deterioration in the mid bass of the speakers in the past year or so and in general they just don't sound as good as they used to.  I don't suspect there's much wrong with the NAKs, I do reset the bias and offset on the amp and also do the needed adjustments for the pre every 4-5 years myself; but the tech may replace a few caps as they are 30 years old now. I'm doing the electronics first so that I can evaluate any sonic difference after the tech part is done. To upgrade the 4's to Walsh 3000 with shipping (to Canada) is $2100 US which equals $2700 Canadian.  That's a lot of money.  If I refoam them it will cost me $400 Canadian including shipping costs.  My question is....... is there sufficient sonic improvement to justify the cost.... and yes, it's a very subjective question.  My ears are not what they used to be, that said my car stereo hasn't degraded in the past few years so I know it's not just my age. All comments are welcome without prejudice.