The C30 will give you great classic sounds, bluesy distortion and a little crunch. The clean channel is nice and it's a lot more portable. There are several other amps that would also fit this bill and a few that would give you those sounds plus the higher gain stuff that are a little more expensive than the C30.
If I were in your position, I'd ask myself these questions:
Is portability the most important part of the decision?
Is the amp's tone or volume level the most important aspect of your decision?
Are the pedals
the most important aspect?
Could you see yourself wanting the JSX again at any point in the future?
If portability is prime, go for the C30 (after investigating a few other similar amp options to make sure it's the one you want).
As for the amp's tone, if you want a versitile amp (without relying on pedals) then you'll probably want to look into some other small 1x12 combos besides the C30, which only does classic and vintage sounds. Take a look at the Rebel 30 when it hits the shelves, or the Bogner Alchemist, or possibly even the Blactstar HT-5 series. These should give you clean to moderate crunch and some hi-gain sounds. The C30 taps out at aggressive blues and and some crunch (think gain on 1-2 of the JSX crunch channel).
As for volume, the C30 still a loud little bugger and you might have trouble reaching the aforementioned crunch at a home levels since there's no master volume...so you're looking at pedals to compensate for anything higher gain. Remember, 30 watts is not 1/4 volume of 120 watts, it's not even close to that ratio when 5 watts through the same speakers is only half as loud as 50 watts.
With the pedals, if you're looking to base your tone from pedals and will get the Satch pedals anyway, the C30 will provide a good clean channel to use as a platform for the Vox line and anything else you want to throw in. The effects loop is fine for your modulation and time based effects as well. It does not, if memory serves, have a level control like the JSX but I don't know if that's an issue for you.
You sound like a huge Satch fan, nothing wrong with that...I am too. If you're playing Satch cover concerts, you should probably keep the JSX since it'll do everything you want for Satch and then it still will allow you to do other music styles with a little tweaking of just it's controls. Just down grade the size of your cab, pull 2 tubes to make it 50 watts and you'll get the mojo going at a slightly lower volume.
With the JSX you'd add the Satchurator to augment its versatility even more whereas adding the Satchurator to the C30 would be to compensate for its lack of versatility. If, down the rode, you'll willing to say that you don't believe you'll ever want the JSX again, go for the total downgrade to a versitile 1x12 after trying the lot of them. If you think there's even the slightest chance that you might want that amp again, get a smaller cab and add the pedals as you have the cash/desire to do so. It will be a lot easier to borrow/buy a new cab for gigs than to repurchase the JSX.
Sorry for the book, brevety is not a strong suit.