Allofs revealed the Bundesliga club are ready to make significant signings in the New Year and will pursue Premier League players should they become available.
United midfielder Kagawa has made just two appearances for the defending champions this term, while De Bruyne appears to be out of favour at Stamford Bridge, having played only three times since the return of Jose Mourinho.
Wolfsburg edged out Arsenal to sign Luiz Gustavo in the summer and Allofs insists they will target players within their budget.
"We want to do reasonable transfers, just like with Luiz Gustavo," he is quoted as saying by Bild.
"That was exceptional in terms of transfer fee and dimension.
"We want to continue a selective reinforcement of our squad. Not in a heave-ho style."
De Bruyne made a substantial impact during his loan spell with Werder Bremen in the Bundesliga last term, while Kagawa has already been linked with a return to Germany with former club Borussia Dortmund said to be interested.
"At Werder, I have seen just how good de Bruyne is, and at Dortmund we have seen how well Kagawa can do," Allofs added.
"If such players are possible, you of course think about them.
"But we should not raise the hopes of our fans. In the end they comment: 'Once again, you failed to sign him'."