The former Dundee United and current Scotland midfielder has indicated his reluctance to sign a new deal with the Scottish champions, and boss Brendan Rodgers seems happy to let the 26-year-old leave.
Transfer fee won't 'break the bank'
Armstrong started just 15 league games last term and this is thought to be the catalyst for his 'big move' to England's top tier. Brighton, Southampton and Palace are all in the race for the midfielder, and with all finishing in similar positions in last season's league table - Armstrong will have a tough choice to make.
A transfer fee of £4 million has been touted, with Armstrong having just one year left on the Celtic deal he signed last summer. This fee won't prove a problem for any of the interested parties considering the Premier League's riches combining with each club's financial security.
The Seagulls to finally get their man?
Brighton were favourites to land Armstrong last summer after their promotion to the Premier League, but the Scotland midfielder chose to extend his stay at Celtic Park after playing time assurances from Brendan Rodgers.
Armstrong will improve The Seagulls' midfield, adding a range of creative and incisive passing as well as a calmness both with the ball at his feet and in front of goal. The ex-Dundee man plays in the 'box-to-box' style, perfect for the fast-paced nature of English football and the fast counter-attacking trademark that many sides deploy.
All three interested parties will be looking to bolster their squads in order to avoid the drop this season, with Huddersfield proving that the television money the Premier League benefits from is levelling the playing field between the 'bigger' and 'smaller' clubs.