How to lower noise floor through mods?

Both caps and resistors will likely increase resolution and lower perceived noise floor. Retaining the tonal balance with these upgrades is a delicate balancing act. Most caps I've dealt with increase brightness to some degree, usually this can be adjusted for elsewhere in the system.

Modding power supplies may be helpful as well, particularly with the transients. I'm upgrading my Cayin's phono pre bridge rectifiers with HEXFRED's and bypassing the electrolytic caps with film caps next week, should have some answers soon. I'm looking for increased transient behavior, specifically more slam.

If you do go the modding route, just remember you can always undo the changes. I've also found modding to be the most interesting aspect of this hobby, really amazing sonic upgrades here! Endlessly replacing components is way too costly and relatively boring.

Mods are the way to go if you have some guts and soldering skills! Practice on cheaper pieces, gradually working your way up to more expensive components.

T bone, just looked at your system, like it! Also looks like you're comfortable with a fair amount of DIY.

The Jadis pre is nice, some VH Audio V-Caps, or better yet, some Duelund copper foil caps (depending on voltage ratings) should both give you what you're looking for. Others may have other cap suggestions, but the two caps mentioned above have to be on anyone's list of primo caps.

The Texas Components Vishay nude resistors (TX2575) are reportedly the best (I'll be making this upgrade soon to the Cayin). The Jadis is mostly point to point wiring which should makes cap and resistor upgrades easier.

Internal wiring would be my last upgrade, I like Mundorf Silver/Gold. Many others to choose from. NOS tubes and different isolation schemes may also prove very worthwhile.

I've investigated replacing the electrolytics in my Cayin power supply with a better electrolytic. Problem is the Black Gates/Rubycons are too low voltage rating (at least I've not found a source for higher voltage) for use in power supplies. I suspect he probably has decent electrolytics in his power supply, likely some better model of Nichicon, bypassing/shunt with film caps may be his best bet. I'm going this route in my power supply.

I believe coupling caps are the biggest bang for the buck, sonically speaking, these should be somewhere near the signal tubes. Not a job for the novice, find an experienced tech.

Atmasphere has it right, start modding with something less valuable. You build up your skills on the cheaper stuff, as you become more skilled you become more confident in working on the more valuable pieces. Read some basic electronics books and ask questions at some of the more technically based audio forums.

You shouldn't be scared to start modding, it can pay off in sonics that fullfill your needs. You just have to understand the hazzards of modifying, nothing is fullproof.

I'm not sure I agree with Atmasphere that only 5% of mods are better, up to now I would have to put my success rate at aprox. 75%, YMMV. Doing you're homework prior to diving in is critical. Also, some equipment is not amenable to modding, the manufacturer may have already used premium parts and/or the voicing may already be optimized. I suspect a coupling cap upgrade in your Jadis will give you what you're looking for.