How you doin guys...

Im looking at purchasing some 15" lightweight wheels 4 my baby... simply for performance driving purposes, hoping 2 hit up a track or 2 in the near future.

I have my eyes set on a certain wheel which is 15 x 6.5 in size. Just wonderin, especially from those who do a bit of track racing or maybe an occasional hill run, what size tyres should i be getting for optimum performance/cornering.

Should i get the conventional 205 x 55 x 15? or as i was told by "tyrepower" employee go a size down to 205 x 50 x 15?

Is there gona be much of a difference or when doin normal daily drivin is the speedo gna b slightly off, any other consequences?

Thanks alot guys any feedback would be much appreciated!