Wooh!  This one should come as a part of a matched set with "Should I buy a new preamp?" and "Should I buy a new microphone?"

...so should you?  Well this is like one of those suspense movies that has two different endings. Use Google and you will for sure find that converters make  "almost no difference at all, certainly less than almost everything else you could spend money on, ....." and "the difference is night and day"; so that's really helpful then!

How about

• If you are a pro, or are working at a pro level then use your ears and decide for yourself.
• If you are new to recording then you have enough other things to worry about, and if by chance you turn-out to be the one in 10 million who instinctively can make mondo-world-class recordings on a dictaphone then it probably won't matter much to you anyway - seriously, stick with what you have until you know more.
• ...and if you are part of the remaining 80%*, the serious, mid to advanced amateurs? Let's go with the classic "it all depends.."
  

Converters don't stand-alone, they have additional circuitry which effects the signal significantly.  converters (small "c" deliberate) in the sense of the bit that actually changes +v to 1/0 or the other way round, should be pretty much of a muchness, but Converters in the sense of the box that you buy and plug things into are subject to all sorts of design and production decisions. The easy and safe view is that unless you feel that your converters are in some way broken (noisy, limited frequency response) then most will be good enough for most things, and you should forget about the whole issue until you notice something that needs to be fixed and have eliminated all the more obvious contenders. 

Except: everything that you record to digital, and everything that you play back from digital goes through your converters.  I drink wine (occasionally) and have a couple of labels that I particularly enjoy. For the odd special occasion, I'll buy a "better" bottle of wine and then find that I don't really enjoy it much because it's different to what I'm used to, and I think that the same thing happens with audio! This is the same reason that folks who listen to all their music as mp3s think CDs are horribly toppy and harsh sounding (not my idea, I read the results of a poll). I am used to my converters, my speakers, my room and that's what I like to hear.  Replace my monitor chain with something better and I'm likely to be polarised to "my-god, it's like day and night!" or "I don't like it, it's too bassy and too toppy and too middly", even though intellect screams that those Benchmark converters and Barefoot monitors must be better than my gear.  Add to this the difficulty of auditioning multiple converters in a known environment with known material and it becomes exponentially difficult. Also bear in mind that it is often easier to discern subtle changes when you take them away.  I remember upgrading from my interface pres and being distinctly unimpressed by the stunning lack of improvement, until I went back to the originals when the difference was clearly, well, night and day!

So it's difficult, but is there an answer?  Yup.If you really need a one word answer then

• if you have mega bucks and you fancy some new converters then buy them.
• if you really know what you are listening to (or if you have access to someone who you trust (possibly not a sales-guy on commission (ah, good old Turnkey!) ) and you have good objective reason that you need better, and you have budget available,  then buy them.  If you are in this category you will know it, ..
  
• ....otherwise (which accounts for almost everyone at the time when they will ask this question), no!

There, I said it!

Of course, you can pretty-well guarantee that your clients will never notice the difference an




* I didn't actually measure this, there might actually only be 3 of us for all I really know!