I'm pretty sure that you can only order The SVS subs direct from them, but check with them directly. They have a customer service department that will get back to you almost immediatly, or you can even call them. Their webpage is svsubwoofers.com, you can get the contact info there. Same deal with HSU. Their webpage is hsuresearch.com. Check out both sites for reviews and stats for the subs, and to look at models I didn't mention. There are people on this board who are fanatical about which is better, but everyone seems to agree that they are great subs. I've only heard the HSU, and if the SVS is close to it in performance (I'm certain it is) then you will not be dissapointed either way. Seriously though, these subs are frigging huge. They don't take up the same small space as a sub you're going to see at Best Buy or Circut City. Think 2 or 3 times bigger in every dimension, and a minimum of 75 lbs, unpacked, and even more shipped. Make sure you have the room.
I really, really like Monitor Audio. You can not order their stuff online through any authorized dealer I know of. Some guys on this site might know, but I don't. If you look at the ad on sound city you'll see that they are retail sales only. My local dealer sells both Paradigm and Monitor Audio, and occasionally PSB. I've heard all 3, but never all at once. The Bronze B4 would be a contendor for the 5T to be fair to it, i don't think it would stand up to well to the 6T. These are supposed to be very differntly priced speakers. THe PSB 6T is on sale because it has been replaced by the T65. Originally the 6T was a $1000.00 pair of speakers, the Bronze B4 is a $700 speaker with one less driver. The 6T is a 3way speaker. One big thing to note here is your personal taste. You may think that the monitors sound better than the PSBs. That is very possible, both are great brands. The Monitors look better than the PSBs in my opinion. I think that the tweeters on all Monitor products are downright sexy, and to put the grills on them is a shame. But if you take a monitor B4, and put it in front of a 6T, Close your eyes and listen to them, I'd take the PSB, same deal for the PSB 5T over the B4 in fact. You on the other hand could be standing right next to me and be blown away by the Monitor Audios. Does that make you wrong? Well as much as I tend to believe that anyone who disagrees with me is wrong in all circumstances, always, regardless of how right they are, no, you'd be right too. As long as you buy quality speakers that sound good to you then you are doing the right thing. I would stay away from the entry level Infinitys and Polks, but keep all you options open. I am always so jealous of guys going out and buying a system. Just do the following and you'll be OK- Audition-as much as you can and when possible directly compare speakers you are considering, Comparison Shop- You can save a bundle this way, dont be shy to tell a dealer you've got someone who will beat his price, these guys do have a healthy profit margin to play with, Demo the speakers will sound different when you get them home, some dealers will let you demo for a week, especially if you are buying a whole system, Enjoy-what you're buying should provide years of fun, don't second guess purchases, you'll drive yourself nuts.
Have fun with it all.