hi,
first of all, with the Decklink SDI you will get HD output, with 4:2.2. No 2K, and no 4:4.4 (that would need a 3G-SDI output, or a Dual-Link output).
Secondly, it’s not the display card that gives you “smooth playback”, it just outputs a signal. You will need a fast CPU, fast storage drives, and a cuda card to get real-time playback.
Anyway if you need a HD output only through SDI, the Decklink SDI is the cheapest choice. But be aware, the only “officially supported” card is the HD Extreme, so as far as I remember I saw here a post, that says that BMD tests new Resolve versions with the Extreme only. Anyway, a lot of people using the Decklink SDI without a problem – including me.
As for the display.. if you’re looking for a grading monitor, you’ll face with an SDI input, I’m sure (and it’s the most reliable connector out there).
But if you just need a good monitor, maybe it’s easier for you to output through HDMI with the Intensity card. I think some use them for Davinci.
But with your price range, maybe it’s more advisable to get a used grading monitor, than a new commercial display. You’ll make decisions given what you see, if you grade 10 films this year, and then one year later you’ll buy a calibrated grading monitor, you don’t want to re-grade everything, just because your old monitor was a bit yellowish in the mids. Just my two cents.
Maybe you find one here: https://forums.creativecow.net/cowclassifiedsforsale