Hi - I have owned 3 pairs of Spicas and still have a pair of TC-50's sitting in a closet at the moment - but if I ever put a system in a smaller room that's what I'd use.
They are basically Midrange Monsters. The midrange and imaging, are IMHO as good as it gets at any price. They have a certain magic there which few others approach. The highs are good but not great, but the bottom end leaves much to be desired. Their main claim to fame in the 80's was true audiophile midrange at under $600, which was revolutionary then. I have not yet found a good, seamless match in a subwoofer. What I would prefer is 2 small subs used as stands with the Spicas above. If you do use a sub, run the Spicas full range anyway - The lows roll off quite sharply on their own, so no need to degrade the signal by running it through the sub's passive crossover.
Back in the good ol days, people would "stack" two pairs and get much better bass response out of them, due to bass "coupling". I once hung them upside down in a kitchen, nestled in the corner where the ceiling meets the wall and they sounded great.
Especially because they had no inline fuses (to keep the signal pure), the tweeters were vulnerable, esp. the TC-50's Audax tweet, and being the nut that I was I always kept a few extra voice coils on hand. The TC-60's tweeters are more robust than the 50's but none of the Spica tweeters are in production anymore - so you're stuck if you blow em. I still have 2 tweeter coils and 2 unused whole woofers as back-up - but when those go, my Spicas will be worthless, at least to me. The major reason for the Spica coherence and imaging (other than optimized crossover design) was that they very carefully measured and matched each unique pair of drivers and crossovers at the factory. I bought my first pair used and couldn't get them to sound "right" at home. After thinking I was crazy for about 6 weeks, I finally called Spica for advice and they ascertained by checking the serial numbers against their testing records that what I had was not a factory matched pair. I spoke to the dealer and it turned out they had bought two pairs at an auction - and mixed them up. So the difference is very audible. (talk about service - even though I had bought them used, Jon Bau had me send them to New Mexico and he replaced ALL 4 drivers and shipped them back to me FOR FREE!)
So as you can see, replacing the tweeters with a different model, or a pair that is not as carefully chosen and matched to the crossover as Spica did, will negate everything the Spica is about.
All that being said - The TC-60 bass is better than the 50's, and the tweeter more robust - so if you place them near the corners of a smaller room, find a good matching sub, and don't overdo the volume or have an underpowered amp causing clipping you should be very happy for many years.
On the other hand, if you can go with a larger speaker at the same price levels, I highly recommend Dahlquist DQ-20's. No need for a sub, spectacular imaging, and incredibly sweet midrange. They're like giant Spicas, and they can be had in mint condition for $600 or less - a ridiculous bargain.
