Obviously I would love to have my Exact Key phrase be the domain. However I have a niche that is LOW and 450k searches a month. If I was to buy domain "ROLLERCOASTERSXXX", would XXX ruin the effect of ranking "rollercoaster"? Or similarly how about "FastROLLERCOASTER". If you just want to rank ROLLERCOASTER, will the other part of this domain make it harder?