I Posed caissons Mah MAC-MS-18B for over a year and I am very satisfied.
Their value for money is more than well.
I feed myself each box with an Inter-M M1000 Bridged.
I put the amps to the max not because MS18B are only 500W RMS into 8 ohms, while the M1000 him under 1000W 8ohms.
At the beginning I feed the two boxes with Australian Monitor C1200 (2 * 600W @ 4 ohms) which makes it well but when I esseillé bridged with the M1000 then I can dir there is nothing better to put a subwoofer in mono, the sound is ten times better, the bass is deeper.
If you have a small budget and you take a eSite MS 18 B, I can tell you that you dir would not be disappointed.