Do I really need a preamp with dac with volume control help

I was putting together a system in a second room and placed order fo Audio Hungary integrated but found out they had no repair center in U.S. and canceled order.

So I ended up buying a Don Sachs with the intention of buying the matching preamp. Im running the RME adi-2 v2 with Teddy Pardo power supply directly into amp. I’m not using phono or CD in this room.

It really sounds very good. Big full detailed with no lack of gain. Not at all like I’m missing anything at least I think so. Then at times I second guess this, I just don’t know.

Long ago I had a PS Audio RAM modded amp with PS audio preamp with outboard power supply out of curiosity I pulled the preamp out of the system ran balanced to phono pre, it had a volume control and everything opened up and sounded much better. Preamp and PSU went in the closet. 

I don’t want to make same mistake I did in the past and spend a bunch of money on a preamp that may not improve things. It could also make things sound worse like my experience with the PS Audio. 

Can someone advise me why I am experiencing this. Should I buy a preamp, am I missing out without having one, I know I can buy preamp and see and if it doesn’t work and then I can sell it but what a pain and expense, thanks for any insight.