I am using Sonar X1 and will be recording electric bass guitar. I will be using a Fender Jazz with tapewound strings. Does anyone have any suggestions or tips on how to best record ( i.e. plug-ins to use, eq, etc. )?
 

Real amp or amp sim? Are you recording the bass direct into the interface or are you using a mixer? Possibly a direct line off the amp. Do you prefer micing the amp only? So many questions to be answered about how you intend to get the bass in to Sonar. More info would help but I would suggest looking around the internet. There are many ways to arrive at your definitive way to get the sound you want. YouTube has a lot of great recording bass videos.
There are many ways to massage the sound after the initial recording is done but it is crucial to get the recording chain right. Are you playing clean pop, rock, country, jazz, etc. or is it totally grunged out metal or punk or alternative.
There will be a lot of different avenues to go in your search for the Holy Grail of Bass Tones.

With out a doubt bass is the trickiest of all instruments to record perfectly. 
My best results are with this in mind :
Bass has to sound good acoustically first,, does it have a good tone when NOT plugged in? 
Technique- No sting buzz, play clean and evenly. 
Pick ups - Boring Pick ups = boring recording. 
Next is optional but will up the ante
A Bass pre amp, I use a TC BH 250
Compression. It might be part of your pre amp. Note, It won't help adding it as a plug in, it will be to late as all clipping happens at your audio interface before the signal is converted. So the Compressor needs to be ahead of the interface A/D. Or you'll want to keep your level down a notch. 
Hi Pass filter- yes, easy to have to much low end which is death to all mixes, go easy on the low end frequencies. 
Always finalize your kick drum track first. Make it perfect. You'll want to crank it up and lock your bass line to it. 

and get yourself a Reddi DI box.

I wouldn't do much if anything to it coming in.  After it is recorded, you can punch it up, but I like to start with a clean DI and go from there.
 
What you would do after would depend on the track.  For example, you might make the kick strong in the low end but cut the bass there and let the bass take the 300 hz range.  You may need a 1K boost to bring it out in the mix, but maybe not.
 
The 1176 compressor in the Pro Channel may help tighten it up.  Surprisingly, there are a couple of good bass presets in EZMIX2.
 
I am not big on amp sims for bass because I prefer a DI sound, but that is just me and your style of music may vary.
 
Good luck.

As stated, a good compressor before the interface would be a life saver. It will catch those nasty peaks before they sneak thru. I have had great results with bass, compressor, interface and nothing else. But, most of the time the recorded track usually gets tweaked a bit with Auddifex GK Amplification Pro. I have always loved Gallien-Krueger bass amps and that plugin is stellar even if it is only 32 bit. The 64 bit update is supposed to be ready for release in February.

Thank you all for your responses.  I'm sorry for my lack of detail as to genre, etc.  I am basically ( no pun intended ) recording keyboard xylophone, djembe and flute.  I also love GK amps, so I will look for the Auddifex GK Amplification Pro.  For recording, I will go direct through a DI into my M-Audio.  I am not mic'ing any amp.  Thank you for your time.
 

I record my bass directly onto My Roland Octa- Capture nice and clean and only adjust the volume and tone on my bass.  After listening to the bass track, I then decide if I am going to add plugins to modify the sound.  There are amp simulators and various plugins that will do the trick...
 
First, play clean and correctly, then modify.
 
Peace.

As long as the signal is clean you can add EQ and compression later. Or, any FX for that matter.

If bass is your primary instrument a good DI is nice.  Interface DI is OK, but something more upscale never hurts.  The Warm Audio preamp has a nice DI while the WA Tone Beast lets you add saturation/distortion to the signal.  Funny, on many styles of music the cleaner settings on the TB are really nice - full and weighty.  The more "colorful" settings get in the way of some of the other instruments.  The TB is what I've been using on DI bass when we record all at once.
 
@