Opinions wanted - speakers

[xneox]

I've got no budget to be buying new gear right now, but I want to be sure I'm using the best of what I have.

I'm currently using JBL Voice for center, Monitor bookshelf for mains (see gallery).

I've got a pair of the infamous Insignia NS-B2111 bookshelf speakers I'm using as computer speakers.

Would I be better off using one of them as the center & picking up another pair for mains ($90 isn't really a budgetary consideration)? I could easily build a stand for one of them to lay on its side as a center if the consensus is that I'd get significantly better performance.