Speakers. The last opportunity to modify your tone. Unlike hi-fi speakers which attempt to create sounds that are true to the musical source fed them, guitar speakers impart their own tone.
Your amp/cabinet pretty much determines three things about what speaker to select; speaker size, impedance and power rating. (See our tech corner article on Speaker Impedance, Power Handling and Wiring
). But the tone is up to you! Speaker replacement is probably the easiest mod you can perform.