A 70-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. His IPSS score is 22 (Severe). Digital rectal examination reveals a moderately enlarged, smooth prostate. PSA is 2.5 ng/mL. Post-void residual volume on bladder scan is 150 mL. According to NICE CG97 (LUTS in men), what is the most appropriate next step in management?