Defending champions Toulouse have led the way by ensuring there will be a capacity crowd of 36,500 packed inside Stadium de Toulouse for their clash with Edinburgh Rugby.
And there won't be an inch to move inside Thomond Park (13,257) when Munster tackle French champions Stade Franà§ais Paris; Stradey Park (10,800) for their showdown with Biarritz Olympique and at the Causeway Stadium (10,000) when London Wasps go head-to-head with English rivals Gloucester - it all adding up to over 70,000 going through the turnstiles.
ERC Chief Executive Derek McGrath said: "We have the prospect of four outstanding matches and, while the quarter-finals are at a 100 per cent capacity, there would appear to be an appetite to fill the venues twice over.
Therefore there is a very strong argument going forward that quarter-finals be played at bigger venues.
"And, for the first time in the nine-year history of the tournament, we have five countries represented in the quarter-finals, underlining the enhanced competitive nature across the board of Europe club rugby.
"I am not that surprised at having four sell-out quarter-finals because attendances in the Pool stages this season have been phenomenal.
"The 72 Pool matches attracted 588,275 fans - a staggering increase of 20 per cent, which equates to just under 100,000 spectators, on the 2002 / 2003 season."