Dan, welcome. Your system looks pretty good and there shouldn't be anything that really needs to be replaced.

On the stereo separation point you mentioned, that's determined by the original recording technique and the mixing used in transferring it to CD. Any competently designed receiver, even the least expensive, has far more than enough interchannel separation; it's rarely even tested for anymore.

As far as a suggestion for something that would really make a difference for $1,500 CDN, my thought would be 50-100 CDs or DVDs.

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Enjoy the music, not the equipment.