I'd say use as little processing as you can get away with.
I think Digital Performer lacks a good compressor plugin (though the Masterworks multiband is usuable), so you either need a good compressor plugin or good outboard compressor. As for a limiter plug you might want to try this one as audio unit, which is free
http://www.yohng.com/w1limit.html Not as good as an L2, but certainly not bad, when not overused.
For both categories, plugin or outboard, there are so many options and just as there are options both can sound good or bad.
If you want to have a plugin compressor, I'd wait till the Sony Oxford compressor is released as audio unit, which will happen soon.
If you want hardware you might want to buy a pair of Distressors, which are very versatile IMHO, clean, or with some subtle distortion or opto-style compression. Or maybe the Tubetech multiband, which is also great, though only one flavour.
And the same goes for EQ's as well, but fortunately Digital Performer 4.5 has a great EQ, the Masterworks EQ, so I'd update your copy if you're still at v4. Another good EQ plug would be the Sony Oxford (also soon available as audio unit), but I think the MW EQ holds up to this one very well.
Offcourse it's not bad to have many flavours, but for most things I think it's better to get right at the source while recording, if it doesn't sound like the way you envision it you better change the mic position, or the mic or the pre.
Reverb. Either get Altiverb or buy a TC electronic M3000 or even better a 4000.