hello guys

his is my setup

1-pioneer 80 prs
2-audison lrx 4.1, 2.9, 1.1
3-hertz mille mlk2
4-hertz xl
5-arc audio subs
6-audison connection capacitor
7- choice between alpine pxa h800 + helix c dsp

the mlk2 woofer is connected to the lrx 2.9 ( active )
the tweeter of mlk2 is connected to the lrx 4.1 ( active )
the hertz xl is also connected to lrx 4.1 ( passive )
the arc audio

Since most my music is in flac and I hate burning cds, and want a fast way to play songs, below is my plan to stop using my pionner 80prs and use the plan below

So I am planning to do the following to use my Lenovo window 8.1 tablet in my car instead of using my HU as a player

now Lenovo windows 8.1 tablet does not have an optical line so I connected my Lenovo via usb to my edirol ua 4fx which then is connected optically to my alpine pxa 800 car processor.

using my lenovo miix 2 tablet ( windows 8.1 ) I don't like the sound I am getting from the edirol ua 4fx as the sound is lacking warmth and detail and somehow sounds weird when connected optically to the alpine pxa 800 i

Is there another sound card or dac I can use instead of edirol that allows manipulating sound and has optical line and gives a warm sound with details

Also I have few questions related to Sound quality:

1- am I degrading sound quality by doing this
2- by using this am I double processing
3- what is the ideal way to connect a window 8.1 tablet that does not have optical to an alpine pxa 800
4- is there anything I can buy instead of the edirol ua 4fx that I have and use instead for optimal sound.