I'd like to upgrade these speakers I have.. but being a first time hi-fi buyer I'm a little skeptical, especially because there are no decent audio dealers around here for me to hear for myself before buying.. I'm leaning toward some Quad 21Ls.. would they really produce an incredibly different/better sound than Cerwin Vega VS150s? would I need to upgrade my amp before noticing? it's a yamaha cr600, I'd appreciate some different thoughts. thanks