Cost to replace BK ST140 in todays $$$'s & quality

I used to own a ST140 years ago, and now yearn
for it again. I know they are available used, but finding one in mint condition is difficult. I would like to replace the 100 watt version that retailed for $550 back in 1990, and was wondering what that level of performance would cost today and what a suitable alternative would be, thanks.