If you anticipate you'll be doing anything with keyboards and MIDI, go in the direction of the Tascam 16X08. The older Tascam 2488NEO Portastudio that I have has MIDI ports which can be used in a limited way for MIDI, but not for MIDI sequencing, which a DAW such as Reaper would do easily (once you get the hang of it). The current DP24/32SD series has no sort of MIDI functionality at all. The Tascam 16X08 appears to have DIN MIDI connectors that would accommodate older keyboards, as well as some newer MIDI controllers with DIN connectors.
The Tascam US1800 headphone output level sucks and I ended up getting a cheap headphone amp, which wasn't a bad thing as it gave me 4 headphone outs versus just the one the US1800. Hopefully headphone out on the 16x08 has a bit more output level.
I've liked the Portastudio concept as I've been using for most of my life back when 4 track cassette tape machines were hot and I've progressed that way with upgrades of various machines to the 2488NEO that I have now and a Zoom R24 (super portable battery operation and can be used as a USB interface) that was added recently for a price I couldn't resist. I did buy a Tascam US1800 interface a while back when it had a rebate and I've using it occasionally with Reaper when the mood strikes me right. Reaper is a good DAW, but I often get stuck trying to figure out how to do something that I usually have to take a time out from recording to Google what I want to do.
DP32SD will give you fairly easy tracking, usable effects that can't be expanded on like with plug-ins and edit functions that won't match what a DAW could do. What you do in the DP32SD can be transferred to the computer and Reaper for tweaking and final output, but this process is an additional step. A few times I've bought my 2488NEO to a friends house to do some recording. Unless you have a laptop, doing this with a desktop is more of a challenge.
I'm not too keen on using a mouse in Reaper, so I picked up one of these to give it more of a Portastudio feel.....
Korg nanoKONTROL2 - Black
Actually a bigger version available now...
Korg nanoKONTROL Studio