Do your Legacy speakers have a built in amp? If so, you can probably get away with a Yamaha RXV 2600 instead of the 4600 if you have lots of cash
.
The HK's are great, but HK is coming out with new models as we speak, and previous year models have had a few glitches (one is called the "18 months slow blow fuse"
).
You can't beat the 7300 for power vs value. Just be sure you have a local HK authorized shop if you go that route. They get expensive to ship for as much as they weigh.
The Yamaha RXV line is expensive because of the lack of online warranties. HK doesn't suffer from the online purchase issues.
Keep an eye on Harman Kardon Direct through ebay. Every once in awhile, they'll have an AVR7300 for under $1000. It's a refurbished unit with a full warranty - the plus being the bugs have been fixed. IMO, that's the best HK to buy, on that has the "twice over." The 635's always go for great deals there, and are easier to find.
http://stores.ebay.com/Harman-Audio_Harman-Kardon_W0QQcolZ2QQdirZQ2d1QQftidZ2QQtZkm
Here's some bench specs on the AVR7300. One of the most powerful 5/7 channel amp sections you can buy in a receiver - period.
http://www.soundandvisionmag.com/assets/download/harmonkardonAVR7300lab.pdf