How To Connect Equalizer To Mixer

I have a Peavey XR600C powered mixer and I'm thinking about purchasing a
good vocal preamp to improve the sound during live performances. In
Sweetwater's preamp buying guide, it states that 'one high-quality preamp
can make your low- or mid-priced mixer much more effective.... You can
alleviate the sonic compromise by adding a good vocal preamp that bypasses
your low-cost mixer's input stage and create a noticeable improvement in the
quality of your mixer'. I must admit that I don't know how to connect an
external preamp to a mixer if the mixer's inputs are to be bypassed. As far as
I can tell, there are essentially 2 ways that the preamp can be joined to the
mixer:
1.) Connect the external preamp to an XLR input on the mixer. In this case,
how will the mixer's mic preamp affect the sound, especially if the mixer's
preamp is of lesser quality then the stand-alone? Also, if the mic and the
preamps are connected in this way, is there a summing of impedances
from both preamps? If so, will this improve the sound?
2.) Connect the external preamp to a 1/4 ' hi-Z input on the mixer, using
an XLR - TRS cable or an XLR - TRS transformer of some kind if the
stand-alone has only XLR outputs, or a TRS - TRS cable if the external
preamp has a 1/4 ' output. How would the sound be affected in this case?
Would there be a noticeable loss of signal or sonic degradation compared
to option 1?
By the way, does Radial or another company make a DI box that works in
reverse, with an XLR input and a 1/4 ' output?
Neither of these 2 options bypass the mixer's inputs, however. What type of
connection that does bypass these inputs is being alluded to in the
Sweetwater article? Thanks for the help.