A 72-year-old man with known benign prostatic hyperplasia (BPH) treated with Tamsulosin presents with increasing lower urinary tract symptoms (LUTS), including poor stream, hesitancy, and nocturia (x4/night). His PSA level is 2.5 ng/mL (age-adjusted range appropriate) and digital rectal examination reveals a moderately enlarged, smooth prostate. His IPSS score is 18 ('moderate'). According to NICE guidelines, what is an appropriate next step in pharmacological management if symptoms are bothersome despite the alpha-blocker?