Goals from Robbie Fowler and John Barnes earned them a 2-1 victory two weeks ago in the second round first leg in Switzerland after Christophe Bonvin had put Sion ahead.
"It would give our whole season, both at domestic level and in Europe, a huge lift," said the Anfield captain.
Liverpool have been widely-tipped as the main threat to the Premiership title ambitions of Newcastle United and Manchester United, but Barnes thinks that being in the last eight in Europe in March will raise their self-confidence.
"It's important we beat Sion and if we do I think that break in the Cup- Winners' Cup will help us," Barnes said. "It will certainly keep our season alive and give us something to look forward to. It will help keep up morale in the dressing-room and that could be invaluable if we are involved in a push for the title."
Barnes, who was outstanding in Sion and in the first round matches against Finland's MyPa-47, believes there is still work to be done. "The Finns were physically more of a test than the Swiss in the first leg," he said. "Sion had more technical ability and we cannot afford to be complacent."
The Cup-Winners' Cup is the one European trophy Liverpool have not won, and their manager, Roy Evans, is hoping to follow the Anfield old boy Kevin Keegan and his Newcastle side by showing that English sides can conquer the best of the rest in Europe, and fill stadiums.
"It was a great win for Newcastle and they played some smashing football," he said. "I would like to think we share the same views, although I am perhaps a little bit more cautious."
n Liverpool are expecting a near-capacity 40,000 crowd at Anfield as a result of a carefully designed package of ticket prices. Their most attractive offer in the competition is a combined adult and child ticket, which costs pounds 18. The youngsters' part of the bargain is pounds 6, but Liverpool have also set aside other seats at pounds 7.50 for children.