No problems
frx026, I see the point your trying to make but splitters are actually the better option compared to pass throughs and line drivers. The signal remains shielded the entire time and isn't run through any components with noise of there own (e.g opamps) in a splitter. If it goes into an amplifier unsheilded (onto the board) with a switch mode power supply nearby and goes through an opamp and out again its going to pick up alot more noise than with a simple splitter.
That said, even if you spent 25k on audio gear I dout you'd hear the difference between a passthrough and splitter anyway. Its a limitation of our ears if anything.
As long as you don't buy absolute shit cable, you'll never have a problem. Any car audio salesman that tries to sell you oxygen free, quadruple shielded, snake-oil-included RCA's is just plain full of crap.