To preamp or not to preamp. That is the question.

There are basically 4 different kinds of preamps.

1. A pot in a box, it can be just a line level resistive rheostat or more favourably, stepped resistors. Totally passive, no mains power.

2. Line level preamp. No gain but a more sophisticated version of the above, using mains input for various functions.

3. Digital preamp, digital volume control. Volume is controlled by manipulating the digital signal in the digital domain. Degrades sound quality by stripping bits.

4. Active preamp. This preamp, whether solid state or tube will add space, resolution, soundstaging, imaging etc. to your system. Unfortunately they are quite expensive. Usually $15k and above.

Only an active preamp is capable of synergising your system, everything else is a poor compromise. 

While I agree with the previous post about the types of preamps that exist, I don't think the $15K price point for No. 4 is necessary.

I have built tube preamps and bought tube preamps and I have rarely spent more than $6K. Particularly, if you search through the quality Used market. A well-made tube preamp should last for many years. Tubes can be rolled/upgraded at will.

In fact, I currently have a PrimaLuna Dialogue Premium tube preamp that was less than $3K. Tube rolled in some NOS Mullard 12AU7's and pushing an NAD M23 SS amplifier. Truly a wonderful sounding system, with a wide soundstage, a bit of warmth, with the minimal distortion and solid punch of the NAD. 

to keep it simple, same number of pieces, perhaps change to an integrated amp (includes preamp) with remote volume and any other desireable features.

you keep the existing amp available for ... or sell it.

Thanks for all the wonderful input. I am fully aware of the limitations of the DAC in the Node 2i as agd 101 pointed out. It's serviceable but not great.

On my main system my upgrade path was Node 2i , then node 2i with a Musician R2R Dac, then Lumin u1 Mini with Musician DAC. The Node was put back into service with this recent second system. 

Lordmelton pointed out several options. Since I do need more gain, option 1 and 2 are out. No doubt a good tube preamp brings much to the table and in my main system I use a Conrad Johnson LS17 line stage into some Quicksilver Monoblock Poweramps.... so I get that. However, with this second system, I want something rather less costly with a smaller form factor due to space/cosmetic considerations. Also I need a remote control. And so I will likely try something solid state, and see if it yields any improvement. There seems to be enough opinion here to support the fact that a preamp will improve things