I am enjoying my analog system, but what can I do to improve?

I would not concern myself about room size, there are great musical encounters to be had, without making the room a reason the experience can't be thoroughly enjoyed.

Near Field Listening is a set up for the Speakers and Listening position that are used by members of the music production industry and any other methods for speaker positioning are overlooked.

Your room dimension form my understanding seems to lend itself quite satisfactory to allow for this method to be intentionally set up.

I have tried a version of near field in my room with ESL Speakers, where the wall behind the Speakers and the listening position are almost equalized in the dimension and the distance between the Speakers and the Listening position are very similar.  A slight change to the toe in of the Speaker is the only change to the stereo configuration for the speaker, but don't think a direct line to the ear is best, find the toe that really satisfies your own preferences.  

There is not any other method I have created to make a being there experience be perceived and believable, and this is a method used for a selection of live albums that really come into their own when replayed with this as the listening set up method.

The real appeal with this as a choice made for a Speaker set up, is that it genuinely does not cost any money, just a little adjustment to the already owned equipment.

If you want to create a space where the speakers are coupled to the room and the room seemingly has no boundaries, then a understanding of room acoustic treatments will be good to get to grips with, or use a modern technology to carry out analysis and suggested treatments. 

@rauliruegas , I prefer arms that are lighter. With lower compliance cartridges you can always add mass. It is much harder to take it away. I never use very low compliance cartridges because they will increase record and stylus wear and generally do not track as well. I go with medium to high compliance cartridges. There are very few ultra high compliance cartridge's available now. Not sure why. Maybe you know. Perhaps it is because nobody makes the ultra light arms they require any more. 

Remember, I own Sound Labs speakers and have been dealing with ESLs since 1978. The X350 will work, probably better than most but the high impedance at low frequencies will stifle it and choke the visceral component important to good bass. With ESLs you have to consider the amp as a component of the speaker. Generally amps with very large power supplies and ultra low impedance output sections will work better. They also have to have very good cooling because of the very low impedance at high frequencies demands high current which produces a lot of heat. The X350 is fine in that regard. Upgrading everything else is important but only applies to records. Improving the amplifier match will make a significant improvement with any source. 

@sheridanmartinj , next trade in the X350 for an XA200.8 and you will make an even larger jump in performance. Do not let the power specs fool you. The XA200.8 is a more powerful amp.

@shinemaster , you forgot Zenith! 

@limomangus , it seems you are a music lover but not an audiophile. Perhaps you are on the wrong site. The vast majority of us can not throw unlimited money at our systems. The trick is making the best system we can afford. Discussion is useful in that regard as well as a lot of research.

Chung, the Allnic L7000 is an outlier. Very few linestages are transformer coupled. 99% are capacitor coupled, some SS designs are direct coupled, and the Atmasphere MP1 and MP3 are unique in usuing a circlotron output stage. Now I leave to you the question of whether Raul’s opinion holds water or not, because I’ve never even heard a transformer coupled linestage, albeit the Allnic has a good reputation.

Also, if you take Mijostyn’s bald pronouncements on tonearms and their design as only his opinions, you’ll be best off.

Chungjh: we have similar room and in my experience near field is the best option .if you wanna try mix tube pre in your system with Pass try Audio Research ref.

Dear @mijostyn  : With a removable headshell tonearm design you always can take away mass, AT/Denon have headshell as ligther as 4gr.-5gr. .

In the other side the 545 review that Soundlabs posted in its site came by Enjoying Music and guess what, the speakers were reviewed mated precisely to the Pass 350 !

@lewm  the issue on the coupled transformer is not rocket science but just common sense that for what you posted I can think is different from mine. That's all. Pun is not intented. Period with.

R.