Transport under 1500 new or used

Firstly, I would strongly recommend that you do not buy anything w/o a rite of return or that can easily be re-sold.
I have tried a bunch of different transports (unfortunately nothing on your shortlist) and have found that many can add midrange glare, lack prat, etc. Some of these are transports that others have raved about and I thought they did not sound very good. There are two transports I have tried that sounded great only they had other baggage like excessive RFI radiation.
Every transport I have owned or tried has benefitted to some degree from a good jitter reduction device.
If you can't find anyone around here that has heard a Northstar transport, just think of what it will be like to try and sell it if it stinks.
Also, I have tried a tube dac, thinking it would have a warm sound and found it to be brighter and grainier than my all ss dac. Therefore, I would not scrimp on a transport, thinking you can compensate for it with the dac.

the Theta data 3 is a excellent transport available used for about $900 here but if the transport mechanism fails you could possibly be up the Creek without a paddle.

A good tube DAC should not act as a filter or smooth things up. It should be fast open detailed but not hard sounding. Midrange to cry for. The transport is every bit as important as the DAC. I wouldn't look for either one to be a filter of any kind. If they are good they should be musical without any hardness without one to tame the other.

Another thought, you might consider the Sony SCD 777ES. Excellent transport. Sacd playback would simply be a bonus.

Try it. You might like it. (especially the quality of sacd. Very close to vinyl. Very close.)

I was pleasantly surprised by its performance as a transport.

I'm using a Kora Hermes tube DAC with a Theta Pearl transport, and even with tubes in the path I don't hear or sense any filtering. In my system I feel the Kora is more open, detailed and refined than the Bel Canto DAC 1.1 it replaced. Plus having the flexibility of being able to try different tubes gives you some control over the character of the sound, especially if you can get your hands on some of the NOS variety.

The Pearl is quite affordable at around $600 used, and uses the Pioneer Stable Platter mechanism. When I switched to this combo from the DAC 1.1 a faint series of clicks has become audible while directly accessing tracks of a CD. They're so faint however, they don't ruin the musical experience for me.

Get a Proceed CDD. Used they are in your price range and they have jitter reduction built in. I was in the same place as you a month ago and got the Proceed. I used a Cal Delta, then tried three Pioneer DVD players (over a few years) and now the Proceed. The Proceed is much faster, detailed, smoother with very deep bass. My dac is an Audio Note DAC1.1x

I have used several transports over the years including Theta, Audio Research, Teac (same as used by Wadia), Pioneer Stable Platter, Top of the line Sony, and Accuphase. For the most part these were used either with Meridian DACs, Timbre (on loan), or Audio Logic. All of these are good transports, but the differences to my ears were subtle. I thought the Sony (same transport in the Accuphase DP-55 and DP-65 that I owned) was better than the Teac. After purchasing my second Audio Logic DSM-34 DAC I decided to try the CEC TL2. Absolutely stunning difference. Until the TL2 I didn't really believe the transport could make that much difference. This is the most analog sounding transport in terms of warmth and is an excellent match for the Audio Logic DAC, which in my opinion has few peers. The Audio Logic is the only DAC or player that I've tried that comes close to the sound of my Well Tempered Reference table. Also, the TL2s build quality is very impressive. I bought mine used in mint condition for $1200 from a dealer advertising on Audiogon. Read Steven Stone's review in Stereophile Vol.19 No.7. I also use a Genesis Digital Lens, which is an absolute steal at current used prices (around $500). Good luck.

Why don't you just get a used EMC-1 MkII. 20kg transport is to die for, and the latest 24/192k DAC is SMOOTH and totally lacking in grain or digititis. About $2k used or $3k new here and there.