Are you overloading your computer?

Hello Blue..
Welcome to the Recording.org forum.

Before I can suggest any DSP cards (?), please, post us more details of your existing system.
As a first advice I'd say, buy a new computer. Even the 350 $ league is just fine for home recording and, if tweaked right, even more.
350 $ is the starting price tag for DSP cards, too (e.g., UAD..excellent! . PowerCore is out..since they are no longer manufactured).
Both, UAD and PoCo, are DSP cards for running Effects on them to take some load off the CPU. Only their own special FX can be processed.
Nothing else can be achieved with them.
If those are what you are looking for, look for a second hand one. The UAD1 cards are quite cheap, now, and come with a nice basic plugin bundle.
Also, always have the music data on a second drive to prevent this bottleneck and keep your drives defraggled.

Not all programs offer real-time effects. They may let you audition an effect but may not play in real-time until you have rendered the entire production. Most average home computers can muster up at least 16 channels of simultaneous audio playback with at least 16 simultaneous plug-ins all running. But it really depends on the program. Otherwise, some of the most important things to consider is, to have the computer properly set up for audio production, it can't be set up as your average Internet and/or gaming machine.

Any external DSP processor you utilize, will have to have USB 2.0/3.0 and/or FireWire 400 or 800 interface to your computer. Otherwise you are talking about dedicated internal PCI style cards and I don't think you'll find much of that without spending some big-time $?

Time for bed
Mx. Remy Ann David