Imre,
Between the Mackie and M-audio, I voted for the MR5 with the purchase of four pairs. For not much more than the MR8, you can pick up the HR824 (original US made, not Mk Ii) on eBay. The HR is far superior. I have purchased sixteen thru eBay for roughly $325 ea. I use the MRs for less important and less demanding ranks.
If you have in mind to use one pair only, I would definitely encourage you to go with the HR. It is very advantageous to use identical speakers for multi-channel arrays, so this may influence your decision. I personally would opt for one pair of HR vs four pairs of MR. The HR also has much better bass and could conceivably be used without a sub which is not the case for the others.
Joe