It all depends on what you're using them for, and I'm afraid I have no idea what one would do with four quarter-track decks. Whatever you're doing, if it works for you, you're all set.
Most studios keep 1/4" and 1/2" half-track machines on hand for a number of uses. Printing 2-channel mixes to 1/2" half-track 15 ips tape can do real magic for imaging. Slap-back echo can be done with a digital delay and digitally emulated plate reverb plugins, or it can be done old school, sending the vocal to tape running at 10 to 20 ips (varispeed is essential), then sending it from the PB head to a plate reverb, and mixing the plate output back in. And there are a (very) few studios who still keep their 2-inch 24-track machines ready for those few artists to like to track to tape.
It's just that consumer machines *are* a hassle. They tend to be hard to work on, and getting parts almost always at some point becomes impossible. Pro machines are much easier to work on, and you have resources like John French at JRF Magnetics who can relap or replace the heads on pretty much any pro machine regardless of age. Quite a number of suppliers are still making parts for pro machines, and the manufacturers generally keep in stock some parts for their machines regardless of age.
Again, it depends on what you use them for, which is something of an unknown. (And I am curious: what do you use tape for in your home studio?)
I *can* say this: if you use tape to record and play back two-channel material, one good 1/4" half-track pro deck beats four consumer decks by a mile. You do not need NR with 15 ips half-track. On pro machines, motors and their bearings are designed for tens of thousands of hours, and now that *all* tape decks are starting to show their age, that matters. With the half-track format, you can keep print-through limited to post-echo by storing tapes tails out, which you can't do with any two-sided formats.
Pic is an Otari MX5050B2-II I restored during my studio assist days as a project to learn how to properly set up and align a deck. It was a good exercise and the results were very satisfying, despite the gazillion hours of use the deck endured. I became a big fan of Otari, as their audio performance is comparable to the Studer B67, but the repro electronics are far less colored. (Studer made the best transports, but their electronics had a very distinctive, slightly warm sound. It's really good on most music, but definitely not neutral.) I also found that parts costs for the Otaris way below Studer parts. On the other hand, once you've worked with a Studer transport, it's hard to go to anything else.
Have fun.
WW
"I'd crawl over twenty miles of bad country to listen to you pee in a tin cup on the telephone." (Jo Carol Pierce)
