I think if your set on the idea of lugging 2 heads around to shows, those 2 would be a great combo. Again take this with a grain of salt, because I've only heard clilps of the stiletto. But it is not unheard of for a guitarist to run 2 different amps to get a huge wall of sound. If your the only guitarist in your band, and you don't mind carrying around an extra head, I'd say go for it! And if one goes down, then just rely on the second one. If you're ever going to record it'd be nice to have both of these to get different sounds, and layering. Also, if you ever get a second guitarist with good chops but no equipment, or one of his amps blows during a show, you have the backup right there, that he/she can easily plug into or borrow. Or lets say your singer plays rhythem on a song or two, you could easily just have him/her plug into your setup. Really the only downside is the added hassle of bringing it/weight (well aside from being able to afford it, but if your thinking about it I'm assuming you can). Having said that, it's not like that downside is terribly small or insignificant either; that really depend on your situation/transportation/setup time requirements etc etc. But if your set on carrying a second head to a gig already, I don't see why you wouldn't at least experiment running both at the same time.
One thing though, you might want something like an Axess BS-2 buffer/spliter instead of just a Y-cable. It has isolated outs, so when you use it to plug into 2 different amp heads, you won't get nasty ground loop hum. Plus it also has a 3rd tuner out, so if you have a tuner it'd be out of your signal path (this doesn't mute the signal to the amps though, so it wouldn't be silent tuning). Also, since its a buffer it's designed to help your signal pass through longer cable runs without losing tone.
Oh one final thought, it'd be heavy as hell, but you could have both heads in a 2 head ata style case, with casters, so the setup/tear down time would be quicker and you'd have it all in one convenient setup. Downside, the weight and the size. It's going to be a heavy mother fucker, weight over at least 100 pounds I'd say, and wouldn't be surprised if it was closer to 125 or more, depending on the thickness of the case. Then again, the casters would take care of the moving it around on flat surfaces, but you have to think of the weight/bulky size for going up/down stairs and up/down the stage.
Good luck