I am currently using a Merkur 23C DE razor. What would be a second DE razor that you would recommend?
My first was a Jagger. For my next few, I went went vintage and actually bught a lot of 4 Gilettes, a Super Speed and three Techs. Then I bought a birth year razor, 1962 Slim. Now I'm waiting to hear more about the Rockwell to see if I want one or not, otherwise I'm done. Read the reviews, do your research, and see what strikes your fancy.
I'd recommend a vintage Gillette adjustable. Fatboy, Slim, or Super adjustable, they all shave great. The black handled super adjustables are a bit cheaper to snag.
In addition to the above named vintage Gillette Razors, I would consider a Gillette New Open Comb razor as well.
Now that you have tried a modern 3 piece razor, why not try something different this time around? A nice vintage SE perhaps or an injector? An Everready 1924 "shovelhead" SE using Gem SS blades gives me a really nice shave. If you prefer to stay modern and want try an Open Comp, the Cadet OC I've found to be very comparable to the Gillette "NEW".
Most any year Gillette super speed would be a good choice. Gillette fatboys and slims are excellent too. I find it kind of cool using a 50+ year old razor that's in better shape than me.
For New: ATT, Merkur 34 or 38c, EJ DE89 Extra Grip, Parker R98. Vintage: any of the Gillette Adjustables. Any razor you choose, first do your research. Ask yourself: Is the razor I'm using now giving me a great shave after I've learned proper technique and have found the right blade? Do I have a light, medium or heavy beard? How much do I want to spend? http://wiki.badgerandblade.com/Double-Edged_Safety_Razors_Ranked_by_Blade_Gap http://wiki.badgerandblade.com/Modern_Double-Edged_Safety_Razors_Ranked_by_Aggressiveness
All great suggestions but I haven't seen anyone recommend a slant. A Merkur or better yet an Ikon 102. Great razors
So OP, you can tell by the answers that just about any razor is recommended! It's a true story though. I started with the Merkur 23c also, and I still love using it today. I tried my hand at a few vintage Gillettes, then move onto a Cadet OC, a Weishi 9306, then moved into experimenting with GEM SE's. All through out I tried the random cheap Chinese razor too. My suggestion is to look around and find the one that catches your eye. That's the next razor you should buy.
I think a slant for a second razor is the best idea. The Merkur is the least expensive and is a comfortable, efficient performer. If you are in the minority who doesn't care for a slant, it is very easy to sell on the B/S/T forum.