Bottom Bracket Identification

I reckon that there is a 99.9% probability that your bike's current BB is an English threaded FSA MegaExo (the functional equivalent of a Shimano Hollowtech II BB).

BTW. IMO, except for cosmetics, you will gain little by changing the current crankset to a SRAM Red GXP crankset ... in fact, again IMO, the GXP may be the worst of the external BB types because (AFAIK) the spindle has two ODs -- 25mm & 24mm -- more of a gimmick which creates an unnecessary proprietary alternative to the "standard" of either a Shimano/FSA BB spindle-and-BB size or a Campagnolo spindle-and-BB size.

Also, if it matters to you, Shimano chainrings have the best ramping-and-pinning ...

• the superior ramping-and-pinning of Shimano's chainrings is undoubtedly to mitigate the maintenance of "dwell" in their STI shifting mechanism.
  

And, a "standard" 53/39 chainring combination will normally shift slightly better than a 50/34 chainring combination ...

Finally, based on MY experience, Campagnolo shifters work better when the drivetrain is under load ... and so, Campagnolo shifters undoubtedly work marginally better in less stressful shifting conditions.

• Campagnolo shifters will index with many-if-not-most Shimano/SRAM drivetrains ...
  

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BTW. If your frame happens to use a BB30 Bottom Bracket & crankset (that's the other 0.01% -- the frame will have a BB30 label indicating if it is so), then you can get frame inserts which will allow you to use a "standard" English threaded BB ...

BTW2. Without putting a caliper inside the cartridge bearing of an FSA/Hollowtech-II BB, I believe that the Inner Diameter of the cartridge bearing WITHOUT the plastic seal is 25mm, so an FSA/Shimano BB might be useable with a GXP crankset by simply removing the plastic seal ... or not!?!

• NB. If you can use a Hollowtech II BB with a GXP crank you may have/need to shim the driveside bearing outward by ~1mm or insert a "washer" between the bearing & the crank's spider.
  

Alfeng,

Thank you for your plentiful and professional response! I will save the $$ and just do a chain ring replacement, since that's what's started this whole deal from the start. Should I look for an upgrade in cranks, will it need to be an FSA specific set? I'm kind of lost in direction, should I want to upgrade to a lighter/stronger set.

FYI. I should elborate & clarify by noting that when I stated that SHIMANO chainrings have the best ramping-and-pinning that I was referring to Dura Ace & Ultegra chainrings, specifically ... in the past, so presumably in the present-and-future, 105 chainrings are the same as Tiagra-and-probably-Soras chainrings.

Shimano Dura Ace & Ultegra chainrings are really pricey ...

One option to consider would be to substitute either a 36t or 38t chainring for the 34t chainring.

BTW. Several years ago, after I deemed that Campagnolo shifters were vastly superior when shifting to larger cogs when the drivetrain was under a load, I decided to test the limits of the front shifting by installing an unramped-and-unpinned (6-/7-speed) 52t chainring on my "test" bike. With the same Shimano 6500 (9-speed Ultegra) front derailleur MY conclusion was that the Campagnolo shifting was superior to shifting with Ultegra 6500 shifter + ramped-and-pinned chainrings ...

• Campagnolo shifters with a 50/34 FSA crankset & the original FSA chainrings + a vintage (c1980) Shimano DA front derailleur yields clean shifts ... the shifting would be marginally better with a 9-speed Shimano front derailleur
  
• with any ramped-and-pinned 52-or-53/39 chainrings the shifting would undoubtedly be marginally better than with the vintage (thin & flat) chainrings
  

Another option for you to consider would be to eventually buy a set of (preferably) non-QS/non-PowerShift Campagnolo shifters (under $200 on eBay) & sell whatever shifters you are currenly using on eBay ... it's an act of faith, but if change your current shifters to Campagnolo shifters then you shouldn't have to worry about which chainrings or crankset you are using in the future.

• a test which has been on the back burner for several years will be to mate Campagnolo shifters with a really vintage, Campagnolo push-rod front derailleur (I also plan to test a SIMPLEX push rod-front derailleur unless the test with the Campagnolo front derailleur is a disaster) ... maybe, I'll get to it this Winter.