Along the same lines, "yet" just further reinforces the initial thought of "cheap and crappy." I get where you're coming from with it, it sounds little too much like, "Nor, really, it's not sh*tty! Trust me! I know it sounds sh*tty, but I swear it's not sh*tty!"

Lead with the best attribute.

"Professional AND affordable design, all under one roof."

I like the concept but not digging the word "cheap" and I'm still not sure what you're selling (even though I know what you're selling).

This.

Design of what?

I'd change that to "Professional AND affordable design under one roof." Two things does not an "all" make.

Fun!

I am betting that your use of "cheap" is intended to convey informal, down-to-earth style. But I'd have to agree that its negative connotations will override that style choice, especially if prospective clients aren't familiar with your personal voice.

CP has it nailed with "professional and affordable design under one roof." Though NA has a valid point that at a glimpse, users will need to know what is being designed. I know that you're going to offer a wide range of services. Maybe you could consider using your well-earned flash guru to add a touch of magic to that slogan by transitioning between the words, like so:

Professional and affordable interactive design under one roof
[a beat, and then dissolve]
Professional and affordable audiovisual design under one roof
[a beat, and then dissolve]
Professional and affordable game design under one roof

And so on. You're multifaceted! Dissolving between what you're offering will show off your diamond facets without overwhelming the eye.