The Hornets are just two wins from another spot in the first round proper – which they reached two years ago – after beating Isthmian south central side Marlow at the second attempt.
It finished 2-2 at the Camping World Community Stadium on Saturday after Marlow found replies to goals by Charlie Harris and James Hammond.
On Tuesday night Jack Mazzone and Hammond struck late in the first half before a Sami El Abd own goal pulled Marlow back to 2-1– only for Charlie Hester-Cook to make it 3-1 two minutes later, a lead they never looked like giving up.
The win was overshadowed at the final whistle by a flashpoint involving a number of home fans which police are invest igating.
Di Paola is delighted to get through to a third qualifying round tie at home to another Isthmian south central team, Hanworth Villa, on September 30.
He said: “On Saturday we were really poor. We didn’t click and Marlow deserved the replay.
"We were 2-1 up in the second half and missed a penalty and it became a chaotic end-to-end game which is my idea of hell on a football pitch.
"We let ourselves down and I politely told the players so afterwards, but the reaction in the replay was brilliant.
"If we’d been 5-0 up at half-time on Tuesday, they couldn’t have complained.
"Harvey Sparks, Charlie Hester-Cook, Danny Barker, James Hammond and Kadell Daniel all had, in my opinion, their best games of the season. When it went to 2-1 it could have been tricky but we got another very quickly. And I don’t think Lewis Carey had a save to make.”
Di Paola is wary of their next cup opponents: “At this stage everyone is dreaming and no team will turn up and just let you win the tie. We’re at home, which is great, but it won’t be easy.”
Nor will the Hornets’ next test, Saturday’s home Isthmian premier clash with Billericay.
It’s sixth v seventh and Di Paola, who has a full squad to select from, said: “It will be about our toughest game so far, Billericay are one of the favourites.”