I would be sure to audition any new speakers against the old reliables unless there is something mechanically wrong with the current setup. While many AV fans are convinced that a new amp or pre-pro will improve the sound it is much more likely that speakers will change the way your system sounds to a much larger degree. As long as the amp has enough oomph to get the speakers to nirvana levels all else being equal the rest is ones and zeros. The source material also has some effects especially in the analog domain. I have always considered that new processors are only needed if some functionality is gained that cannot be ignored and is must have. All things considered, spend the most money getting the best speakers you can afford and an amp which can drive them.