Underspent on speakers relative to overall system?

I bought my current speakers used 18 years ago for $500. Then I bought used speaker cables for them for $550. And as it stands now cost of speakers is around 6%-7%. Not that I cannot afford better speakers, I cannot afford much better speakers, and until I can things are going to be as they are. Just got power cord for the integrated amp that cost more new than the amp, both were bought used of course for $650 and $750 respectively. Nice impovement compared to $800 new cord that I had before. Purist Dominus Ferox replaced Custom Power Cord Company Top Gun. Despite looking wild on paper, the entire system is quite balanced, needs one better interconnect and one more better power cord. After that - nothing until I am ready for new speakers. And then it's all over again, but I am sure the Dominus and Neptune interconnects will stay, as will Nottingham Spacedeck. Arm, cartridge and phono stage will most likely be replaced along with the amp and speaker cables.

Inna said: 

"Not that I cannot afford better speakers, I cannot afford much better speakers, and until I can things are going to be as they are."

I'm guessing I'm operating at a lower price-tier than Inna, but I'm in the same boat. 

'Still using Sound Dynamics RTS-9's that I bought from AudioAdvisor about 17 years ago.  I love their sound, and I think I would have to pay significantly more than the $800 I spent on them for an improvement worth the cost - and I look every week on Audiogon for the opportunity!

Yes your speakers are a very weak link. Lots of distortion and can’t even play at 90 dB SPL without compression and the deviation from linearity plots look absolutely awful at 95 dB SPL. Also that nasty peak just above 2KHz screams that something is very badly wrong with this design. I would steer clear of Monitor Audio in future.

Best get rid of them as soon as you can. As an engineer these terrible measurements should be quite easy to understand. THD + N a mere 30 dB down in the mid range is appalling (my speakers THD+N are -70 dB SPL which is a target you should at least aim for within your budget constraints).

http://www.soundstagenetwork.com/measurements/speakers/monitor_audio_pl100/

Speakers are the most important part of your setup - even with astronomical expenditures on the speakers and your audio room - the room and speakers will likely remain the weakest link in any setup.

So don't waste money on voodoo science cables, and invest in serious speakers.

The biggest potential problem I see with your system is the amplifier and speaker match. They don't exactly seem tube friendly from the specs. Ever tried a warmish ss amp with them? I know many disagree but SS amp and tube preamp I find is a great compromise for me.