The Classe SSP 800 is fabulous for both stereo and surrounds (HT) but is expensive even used for around $3500 and up cause its original msrp was $9500. Eventhough the SSP 800 is obselete and was discontinued last year but its after market resale value is still at around $3500ish and up.
The OP wants an affordable pre pro I’m assuming for under $3k or maybe around $2k. Also not sure what the OP’s budget is?
What is your budget for a used pre pro? If you’re willing to spend for around $3500 I would highly recommend a used Classe SSP 800 or a used original version of Classe Sigma SSP. The original version of the Classe Sigma SSP did retail for $5k new and you can find a used one for maybe under $3k. The original version or version 1 of the Classe Sigma SSP has been replaced by a Classe Sigma SSP Mk2, which now retails for $6k new and is a current model. The Classe Sigma SSP Mk2 is basically the same processor as the original version of the Sigma SSP with an upgraded audio video boards to accommodate supports for Dolby Atmos, DTS-X as well as 4K video pass through, etc, which the original version 1 can’t.
The Classe Sigma SSP is optimized for stereo performance.
Both Classe SSP 800 and Sigma SSP will perform and sound very good in two-channels or when used as stereo preamps.
I would go with the Sigma SSP if I were you as it is more current and has USB DAC port inputs (back & front) and is DNLA equipped which the SSP 800 lacks. They both sound equally good in stereo for stereo music playbacks but the SSP 800 will perform and sound better than the Sigma SSP in surrounds (HT). Actually according to some people that the Sigma SSP actually sounded slightly better in stereo or when used as a stereo preamp compared to the SSP 800 but the difference is subtle. Classe also claimed the same. But the SSP 800 is better for use in multi-channels or surrounds for HT.
However, all Classe processors do not have video processor / upscaler, so Classe simply switches the video signal unaltered and passing it through to your tv display or projector. Both Classe processors also are not equipped with auto room correction software but instead Classe provides manual PEQ (Parametric EQ) which requires proper tools and equipments and knowledge on how to implement it.
What power amp are you currently using or plan on using with the processor? If you go with either Classe processor I would suggest using high end power amps as well such as the ones from Classe amps and alikes in order to achieve overall high fidelity performance of your setup and system. Or if you’re on the budget the Rotel RMB-1585 five-channel amp would also work with either the Classe SSP 800 or the Sigma SSP. The Rotel RMB-1585 retails for $3k brand new, which is quite a bit cheaper than Classe amps.