lack of bass

hello there

i have big problem

first my system

power-arc 75se , pre- arc 5se , transport- wadia 860x , dac-lampizator pacific, speaker -sonus amati aniversario( 4 ohm)

month ago i spoke to arc and told them that my bass is little thin, he told me to try to connect the speaker to 8 ohms becaus they found that somtimes it sounds better,so i did.

it was fantasty!!! suddenly it sound big with alot of weight.

last week i put some music to enjoy my system and it was a nightmare,the bass has lost its weight and detail,it sounds like it is hollow

and un balance from top to bottom.

 i ordered set of tubes to both pre and power from thetubestore, first i replace the pre tubes.... nothing,then the power tubes.....nothing, i tooke from my dealer a shindo pre.....nothing, remiyo kap 777 power.....nothing.

i took my wadia to my dealer and compare it with lampizator computer and they sound the same.

i must say that the tracks were taken from the web so i dont know how good they are.

please......help