This issue is very disc specific. There are a bunch of "multi-channel" discs out there that are no more than 2 channel mixes that have been "transformed" into surround mixes using Logic 7 or another process. There are, however, many other discs out there that were recorded and/or mixed to multi-channel surround sound. To say that you don't need one because you have the other means you're missing out.

If you're going to venture into a sound system investment that takes into account surround sound formats, leaving out SACD and/or DVD-Audio is a mistake. If you're building a system based on two-channel performance, then, by all means, listen and find the processor that gives you the best stereo reproduction for your money.

You say you're a "tweaker." If that's the case, I would go for the processor that features all the most current options. Otherwise, you'll be forever wishing you could try out the "next best thing."