How important is the pre-amp?

WOW mikelavigne ! You’re in rarified air, or rather the stratosphere.

Actually no, just a few miles outside North Bend, way below Snoqualmie Pass, not even 1200 ft, well within the troposphere.

I wont add too much redundancy to what has been said here. MillerCarbon made me chuckle.

But an overlooked fact is that in the majority of cases the volume and balance controls (essentially two sequential attenuators, so the distortions are doubled keep in mind) are one of the most non-linear and distorting parts of the preamp. Most are in fact pretty bad.

In fact, my current design project is a preamp that eliminates traditional volume potentiometers and replaces them with one of two technologies at different price-points, both are substantially better, and both lend themselves to very nice remote control.

Let’s put aside volume control in the digital domain which has an entire raft of issues, but under the right circumstances can be very good. 99.999% of people have never heard those right circumstances.

Your basic volume (or balance) control is a carbon powder strip with a wiper. It is noisy, prone to dust and moisture, and does not track evenly left to right.

The next step up are Noble/ALPS style, which are still carbon powder, but in a plastic carrier. They are smoother, largely sealed and less prone to issues. They are expensive and in doing so track better left to right. They are still very imperfect.

At the top of the food chain are pairs of discrete, precision, metal-film, low noise resistors. You switch in two matched pairs of these for each volume level - maybe 64 pairs. A smaller number suffice for the balance. Stepped attenuators can cost a HUGE amount due to the labor and the 128 position switches, and are large in size, don’t play well with remote control. BUT computers and relays can come save the day ( as i am doing).

In the middle are what boil down to chips with 128 pairs of resistors that can be switched in and out. They are chips resistors, so imperfect, but i speculated that they are better than the lousy alternative. They can be, but if you use them normally or per the data sheet they are truly awful. It took me many weeks to figure out how to us them correctly. (and a really great chip engineer at the fab firm that made me his fun project).  These are a little complex but overall can be cost effective in somewhat reasonably priced designs - the biggest cost being yet another very quiet power supply (or else.....).

So, the little things are way more complicated than you might imagine. Now that i have prototypes floating around, i can’t go back.

By the way, switches have their own issues, and a preamp does have an amplification stage. If its a Phono (RIAA) it has a very complicated amplifier with up to 2,000X amplification which makes noise a (expletive omitted) nightmare.

So yea, all you need to do is be perfect and it works great.

The preamp is the electrical buffer between yourpower amp and line stage components, volume control, and switch between components.  The separation of the preamp from the amplifier made theoretical sense when they contained phono sections for low output cartridges that needed separation electrical fields from the amplifier output.  Adding another another supply, chassis, and cables increases the cost and complexity.  Well designed integrated amps are plentiful, and popular.  Concerning dacs,  be sure that there is a true volume attenuators in the output stage, and not just truncated digital paths

Used integrated amps for ages, till i got my firstwatt SIT-3.
At first connected to dac direct, rockna wavedream dac has some digital volume control.
Loved the amp enough to decide to get a pass XP-22.
The preamp arrived and i got mind blown!
There is "drive" even at lower volumes.
Sound stage expanded in all directions and everything within it separated beautifully.
More details which is counter intuitive! Supposed to be the opposite, but it was not.
Even tone and timber improved.
I highly recommend a decent preamp. Its not just a volume control, I'm a believer now

The preamp is very important. I just purchased a new preamp and it has completely changed my listening experience.  I thought I had a bad match between my speakers and amplier but the problem was the preamp. I found this out my accident. I only purchased the preamp because I was on a buying frenzy. I wasn't expecting a change in the sound signature at at all. If you are not happy with the sound of your speakers try a new preamp.