Recommend a Pre/Pro for $250?

Yup, the best you are going to do at your budget is getting an older Oppo BDP-93 bluray player.  It's not the best solution, but it's the only one that's going to be in your price range.

There are very limited HT pre/pro's that will do DSD over HDMI and they are all going to be in the $1500+ level.  The Emotiva XMC-1 is one that I can think of.

Really, if you wanted something better, then go with a more expensive Oppo 95 ($500+) or an Oppo 105 ($800+).  The "05" models have a much better audio stage.

I didn’t realize DSD was so uncommon. I guess I will not get that in my budget. What flavor of HDMI will I be looking for, then? The Oppo BDP-95 is a great player, but I just don’t have the budget for it.  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.  The Outlaw ICBM sounds great, but wouldn't digital bass management be an improvement, since I could remove the ICBM from the signal path?  It's hard for me to predict, because I've been strictly analog so far.

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.