I am contemplating a purchase of an external DVD/RW. My budget is within $100-160, certainly no more than $200.

Can you suggest a good drive? I am also confused about all specs, like what do all these numbers mean? I understand it's about the speed, but why so many:

Sony DRX-810UL External Dual Layer DVD±RW Writer
(16x/8x/16x DVD+RW, 16x/6x/16x DVD-RW, 8x DVD+R DL, 4x DVD-R DL, 48x/32x/48x CD-RW).

This SONY is on sale for just $99. Some Plextor drives (I hear a lot about them) are sold for about $150, like this one:

Plextor PX-712UF External DVD±RW Writer
12x/4x/16x DVD+RW, 8x/4x/16x DVD-RW, 48x/24x/48x CD-RW

How good is this Plextor drive?

This Toshiba is $130:
Toshiba PA3352U-2CD2 External CD-RW/DVD-ROM Drive. Looks very neat. Anyone uses it?

P.S. I have a Dell PC. On another Dell PC I had problems setting a write speed of an (internal) CD/RW drive made by LG. It would only write at max. speed. Should I avoid LG brand with Dell altogether?

The Plextor 712 is a bit outdated, it cannot even write Double Layer DVDs. Other than that, it has the reputation of being a very solid drive.
You might be better/cheaper off if you buy an external enclosure and put whatever (internal) drive you fancy in it.

My first PX-712A failed after less than a year of moderate usage. Now I am using a replacement unit sent by Plextor. From my personal experience, it has a good write quality on CD-R and DVD±R, but produces many errors on CD-RW and DVD±RW. The error correction is fair and the unit is not very loud (compared to my old LITE-ON that I thought is going to lift-off the first time I burned a CD).
I cannot say anything about Toshiba, but AFAIK, Sony units are rebadged LITE-ONs and LITE-ON produces average DVD writers. Personally, I am a fan of NEC and BenQ at the moment.

Edit: While at it, does anyone know how the PX-608U from Plextor performs?