The fact that you reluctantly sold your other analog gear might make you think twice about selling the spectralis. I feel like everyone sees it and thinks that it's one of the coolest pieces of gear out there, but they're afraid to go out and buy one at the price point. You already have one, so are past that. I think you can just as easily tweak the spectralis like you can any analog gear, it's just all about understanding how to get to each parameter and as quickly as possible. Patching an MS-20 isn't the simplest thing either and that's a pretty highly sought after synth...
My advice when you're stuck not knowing what to make on the spectralis is clear out some junk songs you don't really like anymore and starting fresh. Isolate one oscillator to a filter, make a 16 note sequence, repeat it and just start screwing around with the Time Linearity Modulation (TLM), make sequencer lines for altering the VCO pitch, shape, etc. And just dive in. Maybe you've got all of that down, if you do, I think you'll have fun, if you don't and want help, I'd be happy to explain in greater detail all the steps involved, but you can start making something complex fairly easily.
The last point is this. Let's say you foolishly buy the A4 with your refund... If you love it so much and you want to get rid of your speckie, you'll end up getting at least $1,000 for it. Also, if the A4 is just a cool novelty and you realize you don't care that much for what it adds, you can always resell it. The nice thing about many synths is that they retain their value initially. Also used gear can be bought and sold for similar prices, so you're not out anything more than a "renting fee." You'll have gained the knowledge of the device, learned that you don't need it, and you won't be out a spectralis as well. If you can afford, at that point, both of them... then you can start doing some cool stuff with a really nice and impressive sequencer (spectralis) and a unique analog synth (A4).
Of course, if you just cannot afford it, you know your financial situation far better than any of us do (hopefully).
Good luck
