Perhaps knowing the difference between direct monitoring and low latency monitoring will help a lot in your decision.
Direct monitoring : to be able to hear the audio as you play it. You can even achieve this for units that don't have this option at the front panel, by simply splitting the audio via a DI box, one line goes to the amp, the other goes to the interface for recording (one way). Ideally, you would want to record the audio dry and only apply effects for the line that goes to the amp, sort of a cue-mix for the performer. This is the common way to record when PC / audio interface performance is not great. Latency can be set higher to compensate.
Low latency monitoring : If the system is capable, you can save lots of space / hardware by having the DAW to provide vst effects and channel back the processed audio to the performer (two-way), while still recording dry signal. The processed audio can be routed to the main mix or a separate line out, depending how many extra outs the interface has. The cue-mix can sound the same, as it's using the same vst effects.
Some better interface provides a separate cue-mix/effects option to improve latency. Audio is going to the DAW one way, dry, but the interface provide effects for the performer, bypassing the need for DAW to provide the effects during recording.
Low latency monitoring is most important if you're going to record midi, using a midi controller to trigger software synthesizer, building up one track at a time - dance music, orchestra arrangement,etc.. If this is your main recording mode, you'll want to have a good PC spec, and a better interface, perhaps just 2 or 4 ins/outs to keep cost low.
At the price point of Tascam US 2000, I would personally go with the Focusrite Scarlett 18i20.
From the previous forum discussion regarding Tascam interface (search the forum, you'll get many insights), the US 1800 is preferred over US 2000. At the price point of US 1800, there is no competition that has that many inputs.
The only issue the reviewer at SOS mentioned that can be solved is the driver setting, running at it's lowest latency, which he mentioned Tascam would have an update by now. The other issues are hardware design that can't be changed, such as the way of handling direct monitoring via an on/off switch for each track that does not allow individual track level mixing. And I suspect this is not an issue if you either do direct monitoring on a single track at a time, or you'll do a band recording and you do not need direct monitoring (from Tascam unit) since the band would have amps / PA and you're just DI-ing all the audio to the Tascam.
Mixer based audio interface may also be a solution for live band recording / mixing (such as Presonus StudioLive, Makie Onyx..) as it provides real time mixing / monitoring. There are inexpensive units from Phonic Helix board and Alesis Multimix, but the Alesis MultiMix is no longer in production and the newer Alesis MultiMix FX is USB 1.1 based, backward (only support stereo mix to the DAW).