Aside from the interesting technical analysis given above, to my ears there are consistent sonic differences between the two that are neither good nor bad, just different flavors. I have owned SE systems and fully balanced systems. Most relevant for you would be my current setup, which is a Wadia 861 feeding into a Levinson 383 integrated amp. I have compared Cardas Neutral (or Golden) Reference XLR versus RCA interconnects between the CDP and amp (same length = 1.5M). The Wadia and ML both operate fully balanced. So... IMHO:
Generally the XLR offers more 3-dimensionality and "air" around the instruments, especially with more complex recordings. e.g., with symphonies XLR seems to sort out the soundstage better. But on smaller scale music such as a single guitar, the RCA seems to provide better focus and a more realistic size, whereas the XLR can sound a bit "diffuse". Generally, the leading edge of most bass notes seems more noticeable with RCA, yet the XLR can give better tone/harmonic definition in the bass. For most rock and jazz I like the RCA presentation. For classical I like XLR. Of course, like anything in audio, I encounter exceptions, e.g., even though solo piano is a single-instrument, I prefer the XLR elaboration of its 3-D characteristics and harmonics. My preference can also depend upon the recording quality of the CD. I've found that my impressions of XLR v. RCA cable are very similar to those of Jon Scull in his review of the Accuphase DP-75V CDP (Stereophile, July 2000, see on-line review).
But these differences are less than what you will hear between different product lines of CDP's and amps. If you find a SE CDP whose sound you really like, such as Naim or Cary, don't worry about what you are "missing" by not having XLR. If you find one with XLR outputs, be sure it is truely balanced before investing in an amp with XLR inputs (and make sure the amp operates fully balanced!). One important note, as stated above, a balanced system will be preferable if you must run very long cables.
Generally the XLR offers more 3-dimensionality and "air" around the instruments, especially with more complex recordings. e.g., with symphonies XLR seems to sort out the soundstage better. But on smaller scale music such as a single guitar, the RCA seems to provide better focus and a more realistic size, whereas the XLR can sound a bit "diffuse". Generally, the leading edge of most bass notes seems more noticeable with RCA, yet the XLR can give better tone/harmonic definition in the bass. For most rock and jazz I like the RCA presentation. For classical I like XLR. Of course, like anything in audio, I encounter exceptions, e.g., even though solo piano is a single-instrument, I prefer the XLR elaboration of its 3-D characteristics and harmonics. My preference can also depend upon the recording quality of the CD. I've found that my impressions of XLR v. RCA cable are very similar to those of Jon Scull in his review of the Accuphase DP-75V CDP (Stereophile, July 2000, see on-line review).
But these differences are less than what you will hear between different product lines of CDP's and amps. If you find a SE CDP whose sound you really like, such as Naim or Cary, don't worry about what you are "missing" by not having XLR. If you find one with XLR outputs, be sure it is truely balanced before investing in an amp with XLR inputs (and make sure the amp operates fully balanced!). One important note, as stated above, a balanced system will be preferable if you must run very long cables.