Hi Tuckers,
This is a good question. A pure sine wave inverter can produce very clean power, and can be superior to AC off the grid because there are a lot of noise sources on the grid that can parasitcally feed into your lines. Of course, this depends entirely on location, time of day, etc... YMMV.
There are definite advantages in going with your own solar PV system, because you know that any noise is YOUR noise and a relative constant factor. Thus a specialized power filter can be designed to reduce only the noise products of your inverter, resulting in the purest power. In the not too distant future, I will be working with Jena Labs to adapt their industry leading power filter for some of the more common inverters.
If you move forward with your solar PV system, please keep in touch. I am very much impressed with those who decide to get themselves off the grid, and I would like to work with audiophiles who have done this.
-kevin