Haven't used Sound Forge, but have used CoolEdit a lot. CoolEdit's filters will allow you to boost or reduce all sounds in a defined range of frequencies. I've used it to reduce boominess on tracks or boost the bass on thin tracks or remove hiss, etc. This is, of course, 16 bit editing done to an already mixed, mastered and produced track that's been compressed down to 16 bit for audio CD. I've also used CoolEdit to record and process tracks transferred from old cassette tapes to, to great effect.

So I'd recommend finding out if your version of Sound Forge has similar filters and try playing with them to get the desired effect. Or else, find an old demo of CoolEdit (recommend CoolEdit 96, it doesn't expire in 30 days) on the web and download and install it for use. The program is defunct now, being bought out by Adobe and changed and marketed as Audition. I'll keep my old demo, thanks.