best speaker wire for extra long runs


I have a 45 foot disctance between system and speakers. Currently I use whatever the thickest gauge Monster speaker wire is - I forget the specs. Is there an upgrade option that will not break the bank that would be a really significant upgrade from the Monster for such a long distance? The only option I have seen is from Cardas, but I do not have a sense of whether that would provide a significant step up in sound quality from the Monster. Speakers are Sonus Faber Grand Piano.
gipp
The Cardas Neutral is the best choice I know of. Occasionally a friend of mine has access to used CArdas cables and once in a while, a long set show up. Jallen
Post removed 
With respect to Eric and Mrderrick, I think the OP made it clear he can't relocate his amp.

I'm no speaker cable expert, but I believe that over such a long run, resistance is your biggest enemy. Using the heavy gauge Monster is a good idea, but it may even be worth thinking laterally and investigating stores that sell equipment for PA and concert gear. Speaker cables at live shows often have to run over 100 feet and still maintain quality (audiophile quality I don't know); you may find they sell quality copper in heavier gauge than any hifi store might stock.

Just a thought...
I'm in the same situation as Gipp, stuck with avery long speaker run. I just started a thread in this forum asking about using NM romex cable for speaker wire. I am curious to see where this goes and will probably try it soon unless someone say's it might ruin my equipment or something.
My run was not nearly as long (19'), and it was not for my primary listening speakers; but I have had good luck with Analysis Plus Blue Oval. I'm using the cables with a Creek integrated and Audio Physic Speakers.