Who said “ flat freq response “ is the best?

Speakers posting their frequency response often are challenged by measurement (for example, every speaker reviewed in Stereophile), with peaks and valleys here and there all over their range. This might not mean much if the designer listened to them, which is generally the case. Also the frequency response noted by manufacturers is often utterly incorrect...I have a pair of very coherent, great sounding Silverine Preludes, which list the low end as -3db at 38hz, when at that point they're more likely -10db at least. My Klipsch Heresy IIIs are rated to around 58hz and that's pretty much exactly right...my subs take over at that point so it's all good.

IMO, phase has been ignored because so few people have heard a properly phased system. Designers who don't understand the importance choose to ignore it and the media play along. Few systems are phase correct to begin with and those that are rarely setup correctly. Very few people who buy HiFi ever hear unamplified music in a good hall and thus have no reference to an acoustic space.

The Absolute Sound recently reviewed a time-aligned 2-way loudspeaker with 1st order crossovers. Unless the drivers are perfect, it is simply not possible to achieve minimal phase error with that design.

The AES has an anthology of Heyser's work on Time Delay Spectrometry.
It's long @ 279 pages: http://www.aes.org/technical/documents/openaccess/AES_TimeDelaySpectrometry.pdf 

Stereophile opined "Essential reading for the informed audiophile: the AES anthology of the late Richard Heyser's writings" on https://www.stereophile.com/content/2011-richard-c-heyser-memorial-lecture-where-did-negative-freque...

I prefer flat from 300hz and up

but some bass boost is fun and id like to have a high quality eq to boost my shl5plus in the bass

I think a bass hump was engineered in over the years simply to make bookshelf speakers seem more alive and warm. However, if it's not in there, and more accuracy is involved in the design, you can utilize subs to make up the difference. The bottom line with this stuff is for a speaker to deliver a coherent and reasonably accurate sound that listeners actually like.