Originally Posted by Bond 007
I agree that they are a good speaker. They just don't seem to be compatible with much else. Therefore the age is relevant. He would seem to have to make the entire system of them or use something else. If he just wanted 2.0 that would be an entirely different story. One option that I thought of if he is just totally in love with them even though he hasn't even heard them would be to just get another pair and use 1 as a center channel.
The design of the Studio Monitor 350, 450 and BP6b, BP8b, and BP10b are 8 years old but they were manufactured right up until the 8000 series came out last year. The studio monitors are meant to be used in a 2-channel setting but they can also be part of a direct-radiating surround system or used as surrounds for the BPxb series where using towers is not possible. Definitive continued to manufacture these to give those wanting direct radiating an option for small rooms. Personally, I think that if the OP wants to stick with DefTech, then I'd use BP8b or BP10b for the front and the SM350/450 for surrounds. The problem is going to be the center channel as the matching CLR 2000 and CLR2002 haven't been made for some time. The CLR 2300/2500/3000 came out after these around 2007. Rather than hunting down these center speakers it would be easier to choose a current speaker package, like that Klipsch package.
This is the general agreement on matching centers for DefTech bookshelf or 2-way BP towers.
SM350,BP6b, BP8b ==> CLR 2002, CLR 2500 ( powered 8" sub )
SM450,BP10b,BP20,BP30 ==> CLR 2000, CLR 3000 ( powered 10" sub )
Not sure if this has already been put forward, but HSU Research have complete speaker packages that are fairly reasonable. All their speakers have 6.5" drivers in a bookshelf form factor. No tower speakers available though.