you have several paths to improve the sound, but starting with the speakers is always a solid approach. I would look at what you really want in a speaker, more sensitivity, presence, midrange, tweeter quality, soundstage etc. If you want the best bang for the buck, for $650, depending on your room size, you could get used:
Speaker upgrade?
Hi. I am running some KEF 104/2 with Morel tweeters. Amplifier is Parasound 2250 running through a Harman Kardon 730. The sound is pretty darn good. Bass though might be a little lacking. I have my eye on some PSB Stratus Golds in excellent condition. Speakers look like new but unable to listen to them. Would I be basically going sideways and not gaining much except for lower bass response in the Golds? Price is $650. Thanks in advance for your response. John