A question about coaxial cable?

I have a kenwood ts-850 and a simple wire dipole in the backyard (up at about 25 feet). Right now im running 300 ohm twinlead (basically lower impedance ladderline) from the antenna to a 1:1 choke balun. Then i run a 50ft length of RG-58/U from the balun to the transceiver. I know for a fact that RG-58/U is fairly lossy (but not horrible) for what i want to use it for (which is again the obvious: Most HF frequencies). This may be a stupid question but, I know that all coaxial cables exibit losses when high power current (or any level of current) is sent through it to the antenna (during transmitting) but when very low power current is ped through (during recieving especially from distant stations) are the losses the same? now i know there will always be a loss in signal due to the inevitable impedance of an imperfect conductor, but will the losses increase with the level of current (transmitting VS receiving) or will the measured losses be identical?....i ask this question because I want to listen to some more distant stations and get better received signal strength without messing with my antenna system