By not using the same speaker series, you're opening yourself up to Timber problems. I've learned the hard way that, for me at least, it's just not worth the hassle. If you want to mix and match, I would say that it's absolutely essential that you find a retailer that will let you take a speaker home with you for a few days before purchasing it. If you can't find a retailer that will do that, then I would suggest that you stick with the same speaker series.