I am looking to buy some KRK speakers but really have there basic questions about them. 1) If I were to purchase these speakers would I need to buy a receiver in order to have them run with my computer, or can i directly connect them with the headphone port? 2) I know that these speakers have a few components that you can buy to add on to your system, like the subwoofer. After I have these speakers can I connect that subwoofer or will I need the receiver for that? 3) I have 2 sets of speakers already hocked up through a 3-way splitter to my MBP, will the KRK system speaker work alongside the other two speakers already hocked up? Thanks for the help.