I've heard the same but never tried it myself.
Are you talking outboard synths or VSTs? OB won't strain your computer but you can get legendary synthesis for $50-100 each
if you watch for sales.
You'd probably get better information from sites like Sound on Sound about computer recording. And Invalid Link Removed for VSTs. Just hit those forums. Those people are as helpful in their fields as the people here are about bass.
VSTs mostly, we have a really nice e piano in our place but no synths

