If you like the XD, I'd definitely suggest checking out the M&P. To me it has superior ergonomics. It also has a lower bore axis, so it even has lower felt recoil.
The XD is indeed a fine choice if you choose to go that route. Springfield Armory and Smith & Wesson have the finest customer service in the industry.
Regarding the HKs... everyone is different, but I have owned numerous USPs, USP Compacts, P2000s, and a P30. I like the way HKs look - and I like the way they feel. I generally think they have a sub-par factory trigger. The double action is heavy and usually has a lot of creep. not very smooth like a good(old) Sig. The single action is pretty good though. Usually breaks nice and crisp. My biggest problem with HKs is that I could never nail down how to shoot them well. They're really the only gun type that I'm just terribly inaccurate with. I can shoot circles around the HK with Glock, M&P, Sig, and XD pistols... I'm not blaming this on the gun. They're mechanical accuracy is good... but something about them just never shot well for me. Very irritating because I really like them!
These days I'm mostly sticking with Glocks and M&Ps. I have others, but for defensive/carry use, it's pretty much always one or the other.
Glock 19 G4 BFG | Glock 17 G4 FDE | S&W M&P 22 | S&W M&P 45 | S&W M&P Shield 9 | Ruger GP100 4" | Sig P226 MK25 | Sig P229 Extreme | Sig P320F | Sig P320C | HK USP 9 | HK USP 45 (Tan) | Walther PPQ 9
Daniel Defense DDM4 V4 | Arsenal SGL 21 | ASA SBR | Savage Mark II FV-SR
Mossberg 590A1 20" SP | Mossberg 500 Cruiser