Is there any module with similar functionallity/price in the market today? I mean a cheap mixer with output level and L/R chanels normalized?

Nobody knows?

In the Modules section, search for 'headphone' as a module name.
Make your choice.

Yes thanks. But, if you search for the combination of both "mixer headphone" it only finds the one I posted, but I'm sure there are diferent options which are not showing.

You could still try google with 'site: modulargrid.net headphone amp' and add keywords to thin out.

Well, what I'd like is users advice

Can you please share the full specifications of this module?
What are the specifications for its hardware components?
What are the specifications for its amplification circuit?

http://www.7pcb.co.uk

EDITED Mar 4th 2016, 21:30