Benign Prostatic Hyperplasia (BPH): The patient's age, increased PSA over two years, nocturia, and urinary frequency are consistent with BPH. The good urine stream suggests that the obstruction is not severe, which is also typical of BPH.

Prostate Cancer: Although the PSA increase is concerning for prostate cancer, the relatively slow rise and the absence of other alarming symptoms (e.g., hematuria, perineal pain) make it less likely than BPH. However, prostate cancer must be considered given the PSA increase.
Overactive Bladder: The patient's urinary frequency and nocturia could be attributed to an overactive bladder, especially considering his high fluid intake. This diagnosis would not directly explain the PSA increase but could contribute to his urinary symptoms.

Prostate Cancer with High Grade or Aggressive Features: Although less likely, it is crucial not to miss a potentially aggressive prostate cancer, which could present with a rapid PSA increase. Early detection is key for effective management.
Urinary Tract Infection or Prostatitis: Infections could cause urinary frequency, nocturia, and potentially influence PSA levels. These conditions are treatable and should not be overlooked.
Bladder Cancer: Less common but potentially deadly if missed, bladder cancer could cause similar urinary symptoms. Hematuria is a common presenting symptom, but its absence does not rule out the diagnosis.

Neurogenic Bladder: A condition where a person has trouble with bladder control due to a brain, spinal cord, or nerve problem. This could explain the urinary symptoms but would not directly relate to the PSA increase.
Interstitial Cystitis: A chronic condition causing bladder pressure, bladder pain, and sometimes pelvic pain. The symptoms could overlap with those presented, but this diagnosis would not explain the PSA elevation.