Britt - once of Arsenal and Portsmouth Women - has belted 20 goals in only eight appearances this season after being persuaded to come out of retirement by boss Charlie Smith.
Marsh has 11 in nine matches, after bagging an eye-popping 44 goals in only 18 appearances last season.
But Britt was unavailable for the Trophy tie at Kingsclere, and while Marsh was carrying a slight knee injury.
She still provided two assists, though, as US won 3-0 thanks to goals from Nadina Green, Thia Wright and Abbie Wakley’s free-kick.
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The quarter final has handed US a home tie with Down Grange, who are fourth in Division 1 of the Hampshire Women’s League.
US sit top of Division 2 after winning five of their six games so far.
Boss Smith admits promotion is the main priority this season. ‘One hundred per cent definitely,’ she said. ‘I think the team are far too good for this division, which has been shown in some of our results this season.’
Gosport Falcons are also through to the last eight of the Trophy after Zoe Jessey (2), Leila O’Brien-Knight and Shannen Woods netted in a 4-2 win against AFC Bedhampton Village.
Falcons will now travel to Bournemouth Sports for a place in the last four.