City's Michael Rose was shown a straight red card after bringing down Ben Brereton in the penalty area in the 14th minute and from that moment, it looked to be a long afternoon ahead for Mark Robins's men.
Armstrong - now with seven league goals so far this season - has been a big positive for Rovers and his brace on Saturday makes him the league's joint-top goalscorer, level with Brentford's Ivan Toney.
Blackburn are also the league's top scorers with 16 goals in their opening seven games, and with the addition of Liverpool loanee Harvey Elliott Rovers look to be building a potent strike force.
This won't concern Reading, however, as they now have six wins from seven, with Middlesbrough the only team to take a point from the Royals.
Reading will once again look to their strong defensive unit, who have conceded a league-low total of one goal this season, to nullify a free-flowing Rovers attack.
Blackburn Rovers Championship form: LWWDLL
Reading Championship form: WWWDWW
Mowbray, who was delighted with Harvey Elliott's contributions on Saturday, will likely hand him his second start since joining the club.
Thomas Kaminski will have to be assessed after suffering an injury later on in the victory against Coventry. If he is deemed unfit, new signing Aynsley Pears will be set for his first appearance for the club.
Despite scoring the winner for Reading against Wycombe last week, Lucas Joao had to settle for a place on the bench having been replaced by George Puscas, and Paunovic will have to decide whether to recall the Portuguese forward, due to Puscas's blank.
Aside from tinkering with his front line, Paunovic is likely to name an unchanged lineup.
Blackburn Rovers possible starting lineup:
Kaminski; Nyambe, Lenihan, Williams, Bell; Trybull, Holtby, Johnson; Elliott, Armstrong, Brereton
Reading possible starting lineup:
Rafael; Esteves, Morrison, Moore, Richards; Laurent, Rinomhota; Meite, Olise, Ejaria; Joao
We say: Blackburn Rovers 2-1 Reading
As the league's top scorers welcome the division's strongest defence, this one could easily see both teams cancel each other out. That said, we are backing Mowbray's men - inspired by recent addition Harvey Elliott - to come out on top and end Reading's unbeaten run.