Like Sgower I like to start at the speakers and move upwards as my speakers being maggies, amp choice is based on that. I am very familar with your amp + pre. as I had the 1066 pre. + 1075 amp. and it did a great job on 5.1 + movies but I listened to 2 ch. 98% of the time and in 2 ch. mode it just didn't quite cut it for me compared to a good 2 ch. setup. Cost was also a factor as I was on a bugdet and prefered to have my $$ in a Better 2 Ch. system. I sold my Rotel gear an moved back to a Better 2 Ch. setup and also got a older Pioneer Elite Receiver to do the 5.1 duty for Movies. To me it was a Matter of what was more important to Me 2 Ch.Music or 5.1 because I couldn't afford to do both at the level I wanted.
Like you I found the 1075 amp to be very good for the money and even used it in my 2 Ch. setup for awhile. But found fault with the 1066 Pre. for 2 Ch. Music. If you stay with your 5.1 setup I would look at a upgrade to the Pre. But I would also take your time and do some reseach on different Processors and ask more questions on different forms as well. If you can find a Processor that does a great job on 2 Ch. Music you will have have a great system for both. There are some great deals on some used gear out there but take your time to make the right choice, don't rush into it.
Like you I found the 1075 amp to be very good for the money and even used it in my 2 Ch. setup for awhile. But found fault with the 1066 Pre. for 2 Ch. Music. If you stay with your 5.1 setup I would look at a upgrade to the Pre. But I would also take your time and do some reseach on different Processors and ask more questions on different forms as well. If you can find a Processor that does a great job on 2 Ch. Music you will have have a great system for both. There are some great deals on some used gear out there but take your time to make the right choice, don't rush into it.