Recommend a Pre/Pro for $250?

DSD is almost never found in HT Processors.  However, most of all 2-channel DACs will support DSD nowadays (through USB connection).

In your budget, you should look at an Oppo BDP-93 player.  They are typically priced in the $150-400 range on ebay.  It will support the decoding and playing of SACD discs, including multi-channel SACD discs.  It will also play 2-channel DSD64 and DSD128 files burned on a disc or from a USB drive.  You can also use the Oppo as a preamp/processor because it does have digital volume control (i.e. you can connect it directly to a multi-channel amplifier).

Quite honestly, HDMI is the worst way to transmit audio signals.  I don't have any direct experience with DSD over HDMI, but normal 2-channel PCM as well as old school compressed Dolby Digital and DTS are already compromised by HDMI.  It give you much better sound quality when you transmit these digital audio signals over S/PDIF coax (or even toslink).  The only thing good for HDMI audio is if you transmit the newer hi-res bluray audio formats (Dolby TrueHD and DTS-MA HD).

There aren't really any HT processors that have a phono input section.  The only one that I have ever seen was the original Sunfire Theater Grand back in 1998.  Some integrated amplifiers will have a phono section, but never an HT Processor.

I figure I'll get more bang for the buck if I focus on buying good DSP + D/A hardware which will excel with the two sources I use most, Roku and music discs. This would allow me to eliminate the analog bass management I use now.

Oh, I missed that you wrote this.  If you are looking for something that does everything you want, SACD playback, DSD, playing discs, decoding and playing from Roku, the next best think is the Oppo 103, which is now in the $500 range (if you want one with a remote and all accessories).  There are several on ebay in the $300-400 range, but they do not have any remote or original packaging or accessories.  The Oppo 103 does have an HDMI input that can be used to connect your Roku as a source.  Obviously, it will play pretty much any disc you put in it.  It also has an excellent Netflix client app.

Otherwise, look at a bargain basement HT Processor.  The Outlaw 975 is probably the best for the money and age.  It will not support anything DSD and you still have to have a disc player.  They typically go for $250-350 when you can find them on ebay.  Just keep an eye out and be patient.

At $300, you are looking at the absolute cheapest and used bargain basement level for HT Processors. (the cheapest "new" processor would be the Outlaw 975 for $549).  You can get something better that is much older, such as the following, but at the 10-15 year old range they do have a increased chance of failing.

From audiogon:
Rotel RSP-1067 at $250 (from 2004).
Onkyo Professional PR-SC885 at $300 (from 2008)

From usaudiomart:
Rotel RSP-1069 at $325 or best offer (from 2008)

Please be wary of anything that does not come with a remote because the remote is typically REQUIRED for any kind of setup and configuration.

I will add something here, My friend owns a Vintage Audio shop he's been in business for almost 40 years so knows his stuff, he wont very often touch older HT receivers as they tend to break easily, lost remotes make them unusable, old tech that's so out dated 5 years later that it wont support current standards, etc.  

I would honestly suggest you go mid-fi  receiver in that budget range. many to chose from like the ones I googled below from Best Buy. 

Yamaha RX-V385 5.1-Channel A/V Receiver.
Onkyo TX-SR393 5.2 Channel 4K Ultra HD AV Receiver.
Sony STR-DH590 5.2 Channel 4K Ultra HD Home Theatre AV Receiver.

I feel they will give you the bulk of what your looking for, have all the remotes etc. working, has a warranty and less then $300.  That will open up the door so to speak and let you enjoy until you feel like upgrading down the road. 

glen 

auxinput,
Your suggestion of the Onkyo Professional PR-SC885 is most in line with what I'm looking for, which is high-end audiophile stuff that has depreciated enough for me.
More suggestions like that would help.  Thanks!

That PR-SC885 from audiogon is no longer available.  There's these on usaudiomart:

Onkyo Professional PR-SC885 - $400
Onkyo PR-SC5508 (modified/upgraded) - $350
Rotel RSP-1069 - $325

That's really it right now.