Hi larstusor,
The 3dB-down point at 33 Hz on your Mirages give you some room to work with, so you might end up wanting to leave their signal unmodified and just "add" the sub(s) at a reduced output level, so to speak. Or you can think about crossing them over to the Mirages and reducing their burden if need be...either way would be ok. As for 8" vs 10", it may come down to a toss up, really...two eights might be quicker, but one ten should go deeper. As far as balancing the bass between the two mains goes, it all depends on what frequency range you end up crossing them in at. At about 60 Hz or below the summing of the bass effect will be pretty much nil. On up to around 100 Hz starts audibly introducing the summing effect and above that frequency it starts to become more and more obvious, IME.
Maybe the bigger question, especially in the price range you're considering, is just how flexible the integration is going to be with your mains. Maybe the number one reason for buyer remorse with subwoofers is not that they don't go low enough, but that they don't offer sufficient control over the right parameters to blend properly, i.e. invisibly enough. I'd much rather go with 2 eights that offer flexibility than any ten that doesn't. In fact, personally, as far as I'm concerned, a sub that isn't offering sufficient flexibility isn't really a sub at all...just a waste of time and money, really. If you can't find one of those in whatever price range you're considering, my advice would be to pass until you can maybe move up the ladder just a bit. That said, there are good ones out there. Just look at things like crossover frequency selections...the more individual settings the better...just 2 or 3??...you gotta hope like hell you get lucky with one of them or you're screwed. Digital parameters are worth looking for if you can find them, since they offer a good bit of sonic transparency in the bass region, usually without much drawback, especially if you're not crossing into the mains. But, you may have to either search a while longer for that or be prepared to move up the ladder.
Hope that helps
The 3dB-down point at 33 Hz on your Mirages give you some room to work with, so you might end up wanting to leave their signal unmodified and just "add" the sub(s) at a reduced output level, so to speak. Or you can think about crossing them over to the Mirages and reducing their burden if need be...either way would be ok. As for 8" vs 10", it may come down to a toss up, really...two eights might be quicker, but one ten should go deeper. As far as balancing the bass between the two mains goes, it all depends on what frequency range you end up crossing them in at. At about 60 Hz or below the summing of the bass effect will be pretty much nil. On up to around 100 Hz starts audibly introducing the summing effect and above that frequency it starts to become more and more obvious, IME.
Maybe the bigger question, especially in the price range you're considering, is just how flexible the integration is going to be with your mains. Maybe the number one reason for buyer remorse with subwoofers is not that they don't go low enough, but that they don't offer sufficient control over the right parameters to blend properly, i.e. invisibly enough. I'd much rather go with 2 eights that offer flexibility than any ten that doesn't. In fact, personally, as far as I'm concerned, a sub that isn't offering sufficient flexibility isn't really a sub at all...just a waste of time and money, really. If you can't find one of those in whatever price range you're considering, my advice would be to pass until you can maybe move up the ladder just a bit. That said, there are good ones out there. Just look at things like crossover frequency selections...the more individual settings the better...just 2 or 3??...you gotta hope like hell you get lucky with one of them or you're screwed. Digital parameters are worth looking for if you can find them, since they offer a good bit of sonic transparency in the bass region, usually without much drawback, especially if you're not crossing into the mains. But, you may have to either search a while longer for that or be prepared to move up the ladder.
Hope that helps