For the 7.1 Direct analog input, differences between the two units should be very marginal assuming the 970's analog bass management switch is set to either bypass or HPF/LPF (the "digital" setting is going to bring the 970's DAC's into the picture, which is likely to give the 990 an edge) - for the bypass and HPF/LPF modes, both should perform similarly for DVD-A, SACD, and of course HD optical disc players (Blu-ray and HD-DVD).

I'm curious - are you planning to use analog output from your 45A all the time, or just for the DVD-Audio and SACD (when you are of course forced to by the formats)? The 45A is a good player, but I still normally recommend digital output for Video DVD's. The reason that I typically recommend this is that Video DVD's present such a wide range of audio formats (DD 2.0, DD 5.0, DD 5.1, DD EX, DTS, DTS ES, PCM stereo, ...) that create a great number of opportunities for making use of the 970's surround processing modes (most often Pro Logic IIx, but also Dolby EX and DTS ES). At the very least, I'd suggest running a digital audio cable and doing some A/B testing with a few discs.